Take a look at the "largest wallets" tab on the rich list at Cryptsy, specifically the new #2 (uKFS ...). He's got 8,726+ UNOs in various wallets, but the most interesting part is this:
Addresses 22 with non zero-balance
1589 known
Wow.
Could be bittrex maybe?
Yes it is Bittrex. A lot more than last time I checked on there, someone apparently deposited a few tons there recently...