Screwed over by client, want to warn others

I'm a web design professional and I've been working on a project with a client for the past four weeks. We didn't agree on any payment upfront anyhow, since the project was nearing completion I requested that he paid 50% now and 50% when he thought it was completed to his satisfaction.

Anyway, the story isn't new, I'm glad it wasn't a total waste of time. I can reuse what I produced for him but he seems to have set a plan of screwing people, mostly hiring young talented designers who freelance, then basically refuse to pay. He's one of the wealthiest people in Europe, and I have nothing to hold against him. I'd like to warn others. He's been a real bastard and I'd like to do whatever I can to avoid him using more people. Can I do that without risking charges?

We never wrote a contract or agreed on confidentiality and the email conversations we've had or both mine and his property. Can I publish it all with real names et c?