FD is writing two different mystery novels at the moment, and doesn’t need this plot, which would work for either a book or a screenplay. Maybe it’s already been done, in which case, I’d like to read that book…
The plot: An anonymous fan takes an obscure music group and, via twitter, facebook, a blog, etc ., pushes the group into significant popularity (the early part of the novel/movie would include [perhaps comic] scenes to show how the group’s own publicity attempts aren’t as slick and successful as those of its anonymous fan). The grateful group makes a point of talking about the anonymous fan when interviewed, and eventually starts their “Anonymous Fan” tour, complete with “I’m an anonymous fan of [name of band]. BUT at some point, somehow, the “fan” becomes disillusioned or feels personally dissed. And then, one by one, members of the group start dying. I’m seeing the lead singer’s girlfriend as the amateur sleuth and some nice FBI guy as her foil/new boyfriend… As for the fan, he/she could either be an actual sociopath attracted to the group while idly web surfing, or a member of the entourage who isn’t much noticed.
Sound familiar??