I like changing my logo because it can communicate an attitude, a feeling, a thought, a mood, just about anything.
I also like seeing when others change their logs too. It's another way of seeing a part of the person's personality apart from their experiences.
Since my name is "Caska" and i have many issues of Berserk (the manga she belongs in) on my computer,
i can just go through, and cut out new icons from time to time,
or i can change them up to suit my mood.
It IS much like changing clothes
update 2009: OFC...
I like to change my avatar sometimes based on mood and others just on a whim. It's kind of like changing clothes with me. The name stays the same so, hopefully, my friends will still know that it's me. :D