Oh yes, TTT, my lack of an avatar is by choice rather than an inability to acquire one!
In religious terms, an avatar is the manifestation of a deity whilst, in more human terms, it is the glorification of a principle. In Internet terms, it is just supposed to be a representation of someone.
My problem with them in the last sense is to do with the fact that so many people who DO have one keep on changing it! How truly 'representative' can an image be, if it is so evanescent? Are these people all chameleons?