If I walked into some random cybercafé, paid $5 cash to use one of their PCs, set up an account at, say, mail.ovi.com in Finland, and sent mail from my new account which I never used again, it'd be rather unlikely that anyone could track it back to me unless they could find someone who was physically there when I was and remembered the guy sitting at PC #12. The technical mail headers would generally provide an IP address that tracks back to the café, but unless they had business records that identified the customer, which are unlikely if the customer paid cash, that's where the trail ends.

Or they might burn the info onto a CD and mail it. I don't know how much secret ID info a CD-R burner adds, so if I were serious, I'd buy a $200 laptop at Best Buy, paying cash, of course, or even better a random used laptop at the Salvation Army, burn the CD on that, then accidentally drop the laptop off the end of a long pier.

Setting up a two-way channel is a lot harder, although I suspect that if you told the other party to post the responses on a Facebook page that has a lot of active friends, it'd be daunting to figure out which of the 300 people who looked at it was the bad guy, particularly if he's looking from a different cybercafé.