Support leeches are a fact of life in the open source world.  Some people don't understand how to be worth supporting.  Others are just so obsessed with their own short-term wants that they are willing to destroy the community they are trying to get support from in the process.  Below are my observations, gleaned from years of actual support leech encounters.

Anatomy

There are two subspecies of support leech, however hybrids are not uncommon:

• The clueless support leech is uninitiated in the ways of open source support, and possibly in IRC, mailing list, or forum courtesy in general.  With proper education, some clueless support leeches can be persuaded to morph into community members -- a completely different, non-parasitic, species.
• The entitled support leech is hyper-focused on its own needs, and does not care to make the support process go smoothly for support-givers or others in need of support.  This subspecies is the more persistent parasite (when compared with the clueless subspecies), as even when educated on "helping us help you" or even general courtesy, it will barrel forward, certain that only its own needs could possibly matter.

Habits

The examples below center around support leech behavior in IRC support channels, however the support leech's habits are consistent across support venues, including mailing lists, web forums, IRC, MUC, and user group interactions.  Unless noted, habits below are common among both subspecies of support leech, as well as most hybrids.  The easiest way to tell the difference between clueless and entitled support leeches is to note their general level of politeness, and how they respond to correction.

• Support leeches often require a show of support or expertise before asking a specific technical question.  "Can anyone help me?", "Is anyone there?", "Does anyone use...?", or "Who here knows a lot about...?" are common forms for this demand, but there are others.  The clueless support leech often does this because it thinks such behavior is polite, or because it feels some trepidation about asking its "real" question.  The entitled support leech, in contrast, is motivated by the feeling that its time is so incredibly valuable that asking a detailed question without a promise of help is beneath it.

Community members, the support leeches' non-parasitic counterparts, enter the IRC channel and immediately ask a detailed and complete technical question, so that they may be helped in the most efficient fashion possible.  A typical IRC channel has 2-4 community members trying to support 5-15 users at once, probably while trying to get their own issues handled.  If for each of those 5-15 users we have to go through a round of greeting them, a round of telling them it's okay to ask a question, and a round of explaining that we don't know whether we can help until we know what we're being asked to help with, we're wasting five or more minutes per person, that could be dedicated to support -- 4 volunteers trying to help 15 people over the course of an hour have 240 minutes to go around.  That's 16 minutes per person if we get straight to the support issue, and 11 minutes per person if we don't.

• Support leeches ask questions as vaguely as possible, so that support-givers must interrogate them in the process of troubleshooting an issue.  The clueless support leech has no idea what information is relevant, and so may go the extra mile by including lots of irrelevant information (like what they were eating at the time), while not giving enough information about the problem to solve it.

Asking complete and useful questions is something of an art form, one that is learned with experience (by those not so entitled as to refuse to learn).  However, the more complete the question, the better and more forthcoming a helpful answer will be.  It is important to include at least what operating system the problem system is running, what version of the software in question is being run, versions of dependencies (if applicable), recent changes to the system (this stopped working since I...), and the precise symptoms being experienced ("it broke" or it won't work" are not precise.

• Support leeches generally will not consult existing documentation before asking for help.  Clueless support leeches often lack an understanding of how to find relevant documentation.  Entitled support leeches generally feel that they will dispose of their issue faster with a human support-giver walking them through it, and simply don't care that this takes time away from helping other support-seekers.  When confronted with the admonishment to RTFM1, support leeches often fail to follow the advice.

Community members create documentation so that information will be easy to find and use, and to prevent duplication of effort.  Community members who encounter an issue with a particular technology will check the documentation for that technology to see if an answer can be found there, and then do a web search on relevant keywords, before asking a live support-giver for help.  Exceptional community members document things they have learned, so that future support-seekers can find the information and be helped.

• Support leeches will often ask the same question nearly simultaneously in multiple channels, and/or repeat it unneccessarily.  This is most typical of entitled support leeches who feel that their question is so important that their desire for attention far outweighs the inconvenience to support-givers who monitor multiple channels.  Clueless support leeches display a variation of this habit in which they ask a question in one channel, give up an getting help there after just a few minutes, and then ask in another channel.

Community members will ask a question in the correct venue the first time, and then idle there for at least an hour in case someone becomes active who does know the answer.  A community member will repeat a question only if about an hour has passed, or if they see a known topic expert suddenly wake up.  If their question goes un-answered for a long time, community members understand that no one is active in the channel with the time/skills to answer, and will ask in another venue (mailing list, forum, etc.) or at a time when support-givers from a different time zone may be active.

• Support leeches often go so far as to argue with support-givers.

The incongruity of asking someone for their expertise, and then argue with the proffered advice, baffles me to this day.  However it is a common MO2 among support leeches.  Asking a probing question when advice doesn't seem quite right, or simply not taking the advice are acceptable, but one should not be pugnacious with someone offering their time and expertise to others for free.

• Support leeches are known for PM3ing support-givers without permission.  This is an attention grab made at the expense of others seeking support, and is even detrimental to the needs of the support leech itself -- but support leeches persist in doing it anyway.

Support should almost always take place in the public support channel.  This way support-givers can juggle multiple support requests effectively, and recipients of support can benefit from the input of multiple support-givers.  Additionally, PMing anyone without his/her permission on IRC is a lot like following a stranger to his/her car -- no matter how "innocent" your intentions, you will still give off a creepy stalker vibe.  Always ask permission before PMing someone you don't know well, and only move a support discussion to PM if it either includes privileged information (such as login credentials) or has veered far off-topic from the channel in which it began.

• Support leeches exhibit an inability or unwillingness use the /topic command in IRC to read a channel's topic.  This leads to them frequently breaking channel rules and/or asking questions in a totally inappropriate channel, where their question is naught but off-topic noise.
• Finally, the most virulent form of support leech, the entitled support leech, as well as most clueless/entitled hybrids, are demanding and rude to channel denizens whenever possible.  They fail to internalize the fact that they are asking for free use of others' time and expertise, and that volunteers have no reason to spend their time on those who treat them discourteously.  Free support venues exist because someone finds it rewarding to help others -- the less rewarding the experience, the less support will be provided, either due to community members refusing to subject themselves to entitled support leeches, or to volunteer burn-out.

I sincerely hope that this information will help others in preventing and dealing with support leech infestations before they overwhelm their support venues.  When time permits, I intend to follow up with a post on support leech encounters.

• 1. RTFM -- Refer To the Friendly Manual
• 2. "modus operandi" or "mode of operation"
• 3. Private Message