I don't think they show much more then they did in the past but they destroy movies for many.
Once upon a time, the only way to see a trailer was in the theater, you've would see it what, once maybe twice? Enough to built the interest in the movie and that was it. Now trailers are all over the place, they can be watched and over analyze over and over and over again.
Over exposure on TV spots as also become too much. Last night I had DVR a 1 hour show (which last 42 minutes now a days with commercials) In that one hour, as I skip the commercials I saw and I am not kidding, the TV commercial for Inglorious Bastards 8 times.
Ok I get it the movie is coming out, I got it! All of this over exposure I find's after a while, instead of building interest in the movie, just kill's it.