I feel like it can be hit or miss with trailers. Sometimes way too much is given away, sometimes it's completely obscure and doesn't give the right feel for the movie at all. The trailer for Secretary is an incredibly unfortunate example of that. It completely cheapens it with the weird scene cuts and the quirky music and the narrative text.

I'm not usually a trailer person, I'm fine with reading a brief plotline before deciding if a movie is for me or not.