Celebrity blackmail was all over the news last week. On May 3, 'Bones' star David Boreanaz was forced to reveal his marital infidelities because, he said, a woman was trying to extort him. And on May 4, Robert Halderman, the television news producer who pleaded guilty to blackmailing David Letterman, was sentenced to a six-month prison term.

So why is blackmail -- that most noir-ish of crimes, which sounds like it belongs in a Mickey Spillane novel -- suddenly coming back? And what can celebrities do to fight it?