NY Times Link
Of course, right now it only applies to "sexually dangerous" people, because presumably that's the hardest group of offenses for people to argue against (won't somebody think of the children??), but I think we can all see that if it can arbitrarily apply to one kind of crime, it can and will eventually be extended to others.
Also note that the case in question involved a man convicted not for sexually abusing anyone, but for receiving child pornography. Surely, if there's one crime that justifies giving the federal government the power to detain citizens indefinitely even after they have served their time, a person watching illegal videos is it.