I feel like one of the biggest wallets, if not the biggest is the cryptsy Bitbar wallet.
Remember their wallet went offline around block 135,000ish if I recall correctly.
The bars are still there I feel, there wasnt another exchange to dump on, as BTER volume was shit, and plus their hacking issue.
Last I heard, there is a lawyer in Florida that is filing to represent cryptsys frozen assets, but I do not know if vern has giving over private keys to all the wallets... or in our case, Bitbars keys.