I've been wrecking myself doing fund raisers and pitching in iXcoins myself and all along some rich a-hole (or a hedge fund or bank) with millions of iXcoins has been sitting around just laughing at us.
Those addresses look like an exchange or pools hot/cold wallet - with shuffling funds around to prevent fragmentation.
It's probably vircurex since it was the earliest exchange for iXcoin. Cryptsy didn't open until May 20th, 2013, and iXcoin would have been listed even later. But of course an exchange doesn't actually own all the coins. The coins likely belonged to dozens or hundreds of different customers.
Try thousands or tens of thousands.
Cryptsy could have millions of IXC, I personally, at one point had 500,000 in Cryptsy, before I pulled them to a cold wallet.
Here's the problem with the exchange theory.
These wallets show a very consistent growth in iXcoins.
An exchange would see wild fluctuations as people sell, transfer and withdraw large amounts. Like I pulled out 500,000 IXC in just 1 day and I did the same from vircurex when I moved to Cryptsy.
These wallets are not showing any downward fluctuations. They show consistent and massive accumulation.
And no exchange has ever been that stable. People don't trust exchanges that much.
The pool theory is more likely but that's still a stretch.