The only hijack attempt I've ever experienced was some card fraudsters I pissed off creating a fake paedophile blog under my full name (and then spamming a large chunk of IRC with links to it for a year or so).

Happily for me everybody I've seen comment on it laughed it off as "I wonder what happened to make them that angry but I'm sure they deserved it" - with a few exceptions of people I've previously pissed off who basically said "nah, he's an asshole moderator but there's no way he's a paedo".

And, well, sometimes I -am- an asshole, and some of those times I deeply regret. But reputation can be useful in general.