Currently the max bet in blackjack is 25 BTC.
That's pretty amazing. That's around $3000. With splits and doubles I expect you've seen some huge hands.
We've definitely seen a fair share of big hands! Our max bet in Roulette is 100 BTC, so we see some large wagers there as well.
That's the nice thing about keeping everything in BTC

As the purchasing power of bitcoin rises, so do our effective limits.
It boggles my mind to think about the bankroll required to offer limits that high.
Well, if you look here:
https://bitcointalk.org/index.php?PHPSESSID=63jvb7jar34mtdefttso41v715&topic=75883.0 you can see that some gambling games offer unlimited max bet

)
I don't know of anyone that actually offers unlimited bet sizes. If they do this, they're basically guaranteeing that the house will eventually go broke.
I wrote a post up earlier in this thread which details how we calculate what we set our maximum bet size to, based on the risk-of-ruin:
https://bitcointalk.org/index.php?topic=87656.msg1145478#msg1145478There's a post somewhere in this thread about bitZino's analysis of what max bet they can safely offer. I don't think it talks about their bankroll specifically but it may be possible to infer a ballpark amount based on their current maximum bets. I'll link to the post if I find it.
See the above link - I think that's what you're referring to!