You could complain to their host about copyright infringement and hope they do something. You may be asked to prove that your material was really yours and that isn't exactly easy. Or they may just ignore you in the worse case scenario.
Lawyers? Nah forget about that, it would cost a small fortune and even if you won (a really big if) you'd be in the hole even further.
Of course, you can threaten them with doing so and hope they retract your content.
Really, there isn't much you can do in situations like this. You just have to assume that anything you put online is fair game. 'Tis the nature of the net.
