You could reserve a domain that could pass as a law firm (for example, AndersonSteinbreckandAssociates.com). Then, send an email to everyone mentioned above (registrar, host, thief, PPC engine) and cc: "Ben Steinbreck" at your "law firm." Mention taking legal action if a deadline is not met to your satisfaction, etc.
I know that probably sounds cheesy, but I'll bet that would actually work on a few thieves.
But, as Smaxor and others implied, don't spend too much time on chasing people down. As soon as Thief #1 goes away, Thief #2 will pop up.
Do what you can and move on.