Let's suppose that you had maintained a presence on a domain for a number of years, call it "stonemirror.net".
Let's further suppose that a "troll" (more accurately, an online stalker and harasser) purchases the domain "stonemirror.org" and puts up a pro-NAMBLA web site with your name on it.
That happened to me, and the person who's harassing Rachel Marone — Jason Christopher Hughes aka Michael Rudra Nath — is the person who did it to me.
Suppose that someone set up a Facebook profile impersonating you, and attempted to get your friends and family to add it. Suppose further that he preemptively blocked your real profile, so you could neither see nor report it yourself.
That also happened to me, and Jason Christopher Hughes aka Michael Rudra Nath is also the person who did that.
What's the collective wisdom of Slashdot on dealing with such things?