Do you find it profitable to sue people over projects?

If a lawsuit over a project would be substantial enough to be a credible threat and justify the legal expense, I would argue you shouldn't be outsourcing whatever it is at all--it's too critical if you're in the smaller end of the business world. If you use rentacoder, I think the risk is on your head, and the agreement is clear--they don't get paid if they fail--I don't think you can sue the coder successfully, but maybe I'm wrong.

If you're saying you will get better results with a US coder, that may be true for other reasons (greater loyalty, common culture and language, fear you'll drive across country and find them).

The threat of lawsuit is more relevant if they were to violate copyright and take work done for hire and resell it, or set up their own site to compete with you on your own codebase; this is especially true if you give them access to your systems as part of the process, rather than bring in an isolated component. I agree that failure to deliver is rarely worth the squabble; but for these more extreme cases, knowing that there's legal recourse can prevent problems from occuring in the first place.

the problem with civil action

is that you can't get blood from a stone. If you sue someone without assets or insurance, you probably won't be able to even recover enough to pay the lawyer.

I would argue that it is better to find someone with a good reputation, someone who is careful to preserve that reputation.

and like everyone else said, make sure that the person has a good reputation on the site, that they did projects that were similar to yours in the past, and that they have a flawless reputation