So what does one do in this case?
Sorry folks this one's long winded, but the question was asked.
Laws and procedures vary from jurisdiction to jurisdiction. If it was me going after the thief, and it has been in the past, I'd start with a simple email/letter to the offender informing that I own the copyright for the material, and can prove it, and expect to be compensated for the use of my material for capital gain. I also take this time to cc his service provider/web hosting site. They have a tendency to get prickly when one of their clients exposes them to a potential lawsuit.
If that does not get the offender to initiate a conversation and negotiation, then my next email/letter is the one informing that they are in violation of copyright laws and must cease their activity immediately or face a legal challenge in small claims court.
I also take the time to inform them, that regardless of where they live (assuming in my home country of course where domestic laws can be upheld relatively easier) that I'll be filing the complaint with the local court and thus once served they will be legally obliged to fight the case in my hometown. As the complainant, I get more consideration when it come to venue, so right on outset, the offender is looking at travel to my hometown, the costs for a local lawyer etc.
That is usually all it takes for the faint of heart thief; after all there are plenty other potential victims waiting on the next click of the mouse and I'm begin too much of a pain in the backside.
For those who are really stubborn about it, I look to see what the costs would be to proceed, and if justified, I file a formal charge, through my lawyer, and haul their thieving rump before a judge. Part of my petition includes the cost recovery for my lost profits, legal fees, court fees and punitive damages.
How do I prove my case? Well simply I use one of the more respected (in the eyes of the courts anyway) government institutions; Canada Post. (Being Canadian I use them, if I were a US resident, I'd be using USPS). Before I release any original work that I deem to be of significant value, I burn it to a CD, take said CD to a local post office and send it back to my self registered mail, signature required (Once this is done you can never open the envelope; the sealed, dated, and signed stamp will be useless should the envelope get opened.) By doing this I now have fairly incontrovertible evidence of when the piece was created/shipped. IF my unscrupulous thief should try and claim authorship/copyright ownership, they are going to be in for a shock as I have proof, from a very strong witness (the postal service) of when I created the material.
I have actually had to use this method once, with an outdoor publisher that pirated one of my articles. The magazine in question was published out of the US, and I had sent them an unsolicited article for publication consideration. They politely told me that they did not accept freelance pieces, preferring to write their own articles; thank you much etc, etc. (this is how a freelancer gets work, we write then try to sell the final product)
Six months later, a fairly close copy (some minor changes but not near enough to distinguish it from my original work, appeared in one of their magazines. I was livid. I really didnt care much about the financial side of it, a feature article like that, even it makes the cover (which it did not in their rag), is only worth, at the top end, a couple of thousand dollars. (And besides in the interim, I had sold my original work to a Canadian publisher), but the fact that they claimed authorship really ticked me off. (Besides my Canadian publisher was calling asking if they had exposed themselves to a copyright problem as they had no previous dealings with me beforehand and were concerned that they made a bad decision, so for me, it was also a reputation thing.
It took three letters and one threat of legal action, to get the plagiarists to succumb; they paid me the going rate plus the costs of having my lawyer draw up a few letters, but did stick me with a non-disclosure (hence why their name is not being used). Apparently they were going to start soliciting freelancers and did want me sullying their reputation. Talk about balls.
This particular incident wasnt even about copyright infringement of the written word, but of the idea, and creative thought. They got caught copying my ideas, (and a hell of a lot of my text) and knew that further exposure was going to leave a mark.
So yes, one CAN fight it, but if its just about the money, forget it, youre generally lucky to break even. If its about personal pride of workmanship, reputation, then its up to you how much those are worth to you.