Ha, I like how this turned into "why" instead of the original "how."
I have two accounts, one for strictly LEGO and one for selling randomness or buying. Nothing shady about it. I just felt it'd be out of place if I had a LEGO-themed name and 99% LEGO, but one Barbie or other toy among the mix, so it'd make sense to me. It'd bad enough I have one or two Mega Bloks, but at least those are still bricks.
@stackablesIn attempting to answer your question, my two eBay accounts have different usernames and registered email addresses, but I believe everything else is the same (name, mailing address, even the PayPal account).