So you're kidding about the "ransoming" bit.. but why not have an auction or pledge for 'how much would you pay to know who just posted this post?' and then allow the author to click accept/reveal or no/keep hidden. Could also have an option upfront for disabling the feature (maybe only disabling on the author's end, to ever reveal, but let user's think they can bid it up).

Got me intrigued at least.