Bitfinex is incorporated in Hong Kong. Let us suppose you make a $10,000 wager with them, and they take your money and close your account and ignore your emails.
How do you suppose to get your $10,000 back? Hint: you won't.
"ICBIT currently is in process of incorporating in an offshore jurisdiction."
Bitfinex - The place to trade bitcoins - Easy - Secure - Margin trading, lending market, bitcoins exchange: https://www.bitfinex.com/
ICBIT - Bitcoin Derivatives Market and Exchange: https://icbit.se/
Goodluck.