This might be of questionable ethics, but if you put his twitter handle here, anyone googling for him will without a doubt come across your description. Google loves HN. Mention it on another high-traffic web site?
Send him an email warning him before with a chance to come clean or repair the damage he's done. Also, don't threaten; just write "I will post this on date X, and I'd like to hear your side of the story before then."
The problem is he's incredibly eloquent and it's hard to believe that he's anything other than a decent bloke. It's only by personally experiencing the promise of "I'll check in the completed work tonight" for two weeks that I actually believed my friend.
Also, If I was to in any way publicly denounce another person it would probably have more negative effect on me than them :)
Very fair point and I'm sure my advice is only reasonable in quite extreme situations. Did you try approaching him directly and ask what was up? Also, were completion dates mentioned at all when he was being hired? Maybe he technically didn't do anything wrong from his perspective.
Send him an email warning him before with a chance to come clean or repair the damage he's done. Also, don't threaten; just write "I will post this on date X, and I'd like to hear your side of the story before then."