Excellent points!!!! Trailers are manipulation of audience expectations by the studios. Nearly any type of film can be edited into any other type of film depending on the choice of edits and music used in it, especially when it only runs two minutes.
The Sweeney Todd example is good as I saw it in theatres before seeing the whole film - a musical film, which does not focus attention in the trailer that it is a musical. Of course, I wasn't one of those demanding my money back because I knew it actually was a musical before I went in!!