Read this:
http://www.guardian.co.uk/film/filmblog/2011/nov/11/cinema-3d-video-on-demand?CMP=twt_fd
I picked this link up from someone on twitter, so i can't claim credit for finding it myself, but reading through it, it is all TRUE.
I personally HATE 3D films and i feel it is the real killer of the cinema.
That and the ticket prices and the fact people chew their popcorn really loudly :/
anyways, interesting read!
