Sorry to reply to my own post but have got another minute to add more to this conversation: I run a forum that receives all sorts of legal threats over questionable/defamatory posts. I'd rather not have those dodgy posts on my site and would be quite happy for someone to pursue the authors. When receiving a complaint, I make the effort to reply quickly in each case outlining the legal options. Surely OKCupid are in a similar position - they don't want this sort of junk on their site; if they can provide a quick piece of info and then stand out of the way while the OP pursues the perpetrator, all's well IMO.