This trailer reminded me of all the foreign film trailers. No one talks in it because it wouldn't be english and might turn people off if they knew so all they do is play some kind of music appropriate to the theme of the movie (scary, action, drama, comedy) and just play clips of the movie with people doing stuff and a narrator putting in his two sense about the situation in the movie while repeating the title 10-20 times in the description in case anyone forgot.

500 Days of Summer
Teaser Trailer
(1:39)