As far as ebay goes, I created my username for 
that when my interest in Egyptian stuff was 
greater than my interest in anime. ^_^ I use it 
occasionally for some forums, but very rarely. I 
also have another handle that I tend to use 
primarily for fancels... I like to keep my 
production art self and my fancel self separate.

My two main handles are "Bottou-chan" and "Cres". 
Originally, Bottou-chan was just something I used 
for the Flame of Recca fandom. Cres was what I 
used in the Sailormoon fandom, and for my PBEM 
RPG's. Because I happened to know some cel people 
from the Sailormoon fandom, it ended up being my 
cel handle as well. I've since acquired another 
PBEM handle that I use mostly for non-anime 
PBEM's.

When I buy something from someone on the forum, I 
usually sign off with my real name, and identify 
myself as "Cres on the Animanga Forum" with my 
gallery URL. When I buy something from ebay, I 
don't tend to do that. If someone asks me if I 
have a gallery so they can visit their cel later, 
I'd be happy to share the URL with them, but ebay 
generally has more of a "I want to get rid of 
this" sort of feeling to it, rather than the 
warm, fuzzy, "I need to find this a good home" 
feeling that you get from a collector you know on 
the forums.

So, yeah. I probably have five or six different 
handles that I use, but they're primarily divvied 
up depending on what I'm doing at the time.