An old coworker of mine got into a disagreement on some fish/water tank and terrerium message board (lol seriously). He pissed off the wrong person, enough so that the guy sent an email to our boss pretty much making up allegations of my coworker being racist and misogynistic, which couldn't be further from the truth. There are some psychos out there, man. He ended up taking the case to the police, who sorted it out.
Wow, there really is a message board for everything.