I think you'll find that the UK sites are about to start doing the same. I think Gala started blocking US players a few months back (goes to check blog) and I've heard rumblings there'll be more of the same from other sites.
I know, I've been hearing about this too. It's just about the most ridiculous thing I've ever heard. As if playing bingo online hurts anybody. There is most certianly such a thing as going too far.
I've already had one account deleted. VERY frustrating.
Why are they terminating American accounts? I am so out of the loop.
It's down to George W's UIGEA - the Unlawful Internet Gaming Enforcement Act which came in at the end of last year. You can read more background on it here.