The the "predator" doesn't even know picard's real name (or address or phone #) how can he be a credible physical threat? This presumes that picard is correct and that the other guy really is in the dark. Maybe I'm naive but it sounds like BS to me.

That really depends on how good a hacker the 'predator' is or what level of experience the 'predator' has in using social confidence methods to gain confidential information.

Get hold of someones email address, you have the domain, once you have the domain you have the ISP, once you know the ISP and can get by the security question by just ringing their technical support desk you've got the address and even the phone number i.e the ADSL number. I'm constantly surprised how many times the right answer to 'whats you favourite colour?' is 9 times out 10 the colour blue. And with the address and the password to the mail box, it could even be possible for the 'predator' to hijack the 'victims' identity. Things get even easier if your details are on a social networking sites such as Facebook or MySpace.

I think you should agree to meet him, and then kick his butt!

Seriously, if complaints to the host or admin do nothing, then just ignore him. Yahoos like that are all talk.