About 25% of the population gets headaches from having to focus and converge at two different distances. Since you never have to do that except for some kind of optical illusion like a 3D film that is not going to go away.
There is also a problem with children under 6. Watching can mess up the development of their vision.
http://blogs.wsj.com/digits/2011/01/05/toshiba-echoes-nintendos-3-d-warning/ So like the last two times they've had a wave of 3D movies I expect it will be a fad.
