Yes. This kind of vigilantism has a way of backfiring. What is wrong of getting a title in court and sending the sheriff to take pledges? In fact, I never had to go that far; people have always paid up when I called, asking if their address was still good to serve court papers.

That was my worry with the "will use my considerable SEO skills" part. I would leave that implicit. Just mention that you are angry about the situation and have put up a page explaining your grievance to the public (which is legal), and put the ball in their court to attempt to rectify the situation.

How? This is like telling someone who stole your car that you expect it back or you'll call the cops...

It would only matter if it comes out in court, as that's the only place that claim would have any leverage. There's practically zero chance of that happening, they would settle faster than it would take for the ink to dry, so soft threats like these can be very effective.