Good question!
We developed a site for an American Reverend in Florida. We didn't take any money up front (which we usually do!) as we foolishly thought such a person could be trusted - we put the site on a test domain for her to view. Basically, she downloaded the site and put it on a free hosting account. She won't answer any e-mails or communication and obviously won't pay anything.
We got her kicked off three free hosting accounts when we reported her for website theft (Yahoo (twice) and Bravehost). She's now put it on a free Netfirms hosting account. They won't remove it until we get a court order.
Basically we would have to goto the expense of getting a court order as a UK business against an American civilian hosting a stolen site on a Canadian web server.
The Federation of Small Businesses advised us against it due to the potential expenses. So basically, she's got away with it.
Not the behaviour befitting a reverend!
The question is, what would you do to stop this kind of piracy if it happens to you, without getting into a lot of expenses, which small businesses cannot finance?