I am sorry, but this guy is way out of line here. Legally I have no idea, but morally, I do. I mean, go to the place and talk to someone. Or take down the site. Don't start a campaign for your feelings.
edit: On second thought I was eating a restaurant when their televisions turned black and the screen came up with a pay your bill now notice. Every screen in the restaurant. So I guess maybe this is the tactic.
I absolutely agree. I've been in this position as a frontend dev many, many times. And that's WITH a decent contract, no bad gut feeling, great communication throughout. Ultimately, I can't control whether a client feels like paying my invoice or not. I commend this developer, he's done something I've always wanted to do.
Saying that he's out of line or amoral implies that you have an intimate understanding of the situation and that you've weighted that he doesn't have the moral grounds for doing this, which you might agree is disputable.
In my opinion, the only reason this tactic is not recommendable is that it's not deemed acceptable practice from a professional standpoint, and I believe that this is mostly a cultural thing. Everybody says it's wrong, so it must be wrong.
Think about it, if tomorrow all service providers developed a mindset where this kind of shaming in an attempt to collect from deadbeat clients became standard practice, nobody would be advising against it anymore. This is consistent with a lot of everyday nonsense that pass for acceptable, just because that's just the way things have always gone.
I'm not convinced that there aren't places in the world where this is seen as perfectly ok and maybe even expected.
At what point do you stop providing the service (or allowing the deadbeat client to continue to get the benefit of the previously provided service)? 1 week? 1 month? 1 year?
The TV signal issue - how many "you didn't pay" emails and phone calls and written bills did they get before it was turned off? And consider this - if the TV just went dead, people would be calling/complaining "my service is dead!" This is a faster way of telling them why it's dead. The fact that someone was broadcasting to their customers was their own fault if they got embarrassed by it. I would hazard to guess they were probably only licensed for one set, and they were splitting/copying the signal to multiple TVs as well.
edit: On second thought I was eating a restaurant when their televisions turned black and the screen came up with a pay your bill now notice. Every screen in the restaurant. So I guess maybe this is the tactic.