It's quite incredible isn't it, but I can assure you that it really does happen.
I've heard that he has a massive mining setup and mines huge numbers of coins.
This information is publically available on site.
biggest cumulative gains in last 24 hours
+--------+-----------------+
| uid | profit |
+--------+-----------------+
| 441586 | 602.70617183 |
| 441445 | 120.29725771
I hope you stuck around for a few days...
+--------+-----------------+
| uid | profit |
+--------+-----------------+
| 1337 | -2,190.00000012 |
| 449038 | -22.44000000 |
The same guy who won the 602 BTC lost 2190 BTC yesterday, into a 37k bankroll, giving everyone invested an almost instant 6% return on investment. After losing, he said:
(1337)
ie. this wasn't a serious amount for him - it's just play money.
I hear he's collecting "investments" from people to stage an attempt at a comeback. Whether to stay in the bankroll for it or not is up to you.