This seems very unprofessional and amateurish - on the part of the web developer. Yes, maybe the client didn't pay, but resorting to this type of public lynching will a) kill any remaining chance of compensation/reconciliation and b) probably damage the reputation of the web developers.

I've had my fair share of clients who didn't pay for various reasons. Sometimes, small claims court was in order. Sometimes, having patience and giving a struggling client time (literally almost 5 years) led to a payment in full (plus interest!) completely out of the blue. The guy's business picked up, and now he's still a super happy client.

What goes around comes around.