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: