The domain seizures are very troubling, though.
Edit: There seems to be some dispute over where it's a crime to "participate" in different US states, but for the purposes of the "customer assests seized", the transaction is illegal, so it's to be expected that the "cash is locked up" as the result of government action.
http://en.wikipedia.org/wiki/UIGEA
UIGEA "prohibits gambling businesses from knowingly accepting payments in connection with the participation of another person in a bet or wager that involves the use of the Internet and that is unlawful under any federal or state law." but does not make it a crime for a citizen to engage in the activity.
http://www.gambling-law-us.com/State-Law-Summary/
You are right though, the UIGEA makes it illegal to transfer money from a US citizens account to an 'illegal gambling operation.' It doesn't actually define what an illegal gambling operation is.
I'm not 100% sure as it's been a while since I've kept up with this but I believe that Poker has always been in a sort of gray area. I think there is suppose to be a distinction between games of chance and games of skill. In the past only online sports books or true online casinos had ever been prosecuted in the US.
If they did, smart professional players like Durrr and Ivey wouldn't keep multi-million dollar bankrolls online that are subject to loss at any time.
That's just common sense.