Threadjack here, but I think the times that technique does work are the times when it adds something narratively to the episode, rather than simply being in there for maximum melodrama. There's an episode of White Collar that used it to good effect too, I think -- I'm not sure if this is one of the ones you've seen, but it opens with a flash-forward sequence, and as the episode builds to that point, you start to realize that what you thought you were seeing in the opening scene was, in fact, the opposite of what's actually happening. Played straight, though, it's generally just an annoying ploy to keep the viewer from switching channels.