So what's with all the vampire detectives?

I've been seeing all these TV ads for the upcoming series, Moonlight, which features, you guessed it, a vampire detective. Does anyone actually think this is an original idea? Does anyone remember Forever Knight? I know that's a blast from the past that only ran three seasons, but the general concept was resurrected for Angel, which lasted five. There's probably other series of a similar nature that I'm not aware of. (And please let me know about any I haven't mentioned!)

So what's the appeal? I'm not being critical here; I'll be eagerly checking out the series like many, many others. I'm just curious as to where the draw comes from. Maybe it's just the vampire factor. A thesis could be written about our attraction to children of the night (if one hasn't been written already). It might have something to do with the heady mix of danger and physical intimacy.

Regardless, I'm certain many of us will be watching the premier of Moonlight in the hope that it doesn't suck (I know, I know, bad pun...).