Well whaddya know? Here's why the FBI shut down the top poker sites:

http://www.washingtonpost.com/blogs/post_now/post/internet-gambling-is-coming-to-dc/2011/04/13/AF62F4UD_blog.html

The District [of Columbia] is becoming the first U.S. jurisdiction to allow Internet gambling, trying to raise millions of dollars from the habits of online poker buffs and acting ahead of traditional gambling meccas like New Jersey and Nevada.