Let's take the upcoming movie 'The Wolverine' as an example. Besides having numerous different versions of the actual trailer it already has a Vine trailer for the teaser trailer followed up by the full length teaser trailer.
Why do we suddenly want/get so many trailers for one movie? In the past one trailer was always sufficient, but it seems that with the rise of the internet movies tend to release more and more trailers. Is it a way to get people to talk about their movie? Or do the movie producers just think more is better?
I honestly don't think any moviegoer is excited about seeing so many different trailers from the same movie. The trailers basically show every good moment from the actual movie. The amount of times I've watched a movie and recognized at least 60% of it from the trailer is getting ridiculous. And even worse are the trailers that pretty much show you the entire movie in chronological order, like the trailer for the upcoming movie 'Carrie'
Now it's not all spoilers and ruined movie experiences. Take the official trailer from 'Thor: The Dark World' for example. That's a decent trailer, it doesn't give away much but it does make you excited. You see Thor scream "noo!" but you don't know why (it's not hard to guess however). And that's what a good trailer is about, getting you pumped for the movie. Not spoling the entire plot and storyline.
This is however only the first trailer so who knows, they might still fuck it up.