Now that 3D is the big (but potentially transient) craze, there's tremendous pressure on film producers and distributors to release all their new films in 3D, whether or not they were shot that way. The recently-released remake of "Clash of the Titans" was shot in 2D, and then hurriedly digitally converted to 3D in an eight-week process. As widely reported, the results were far from impressive; most reviews said that the characters and creatures looked like 2D cardboard cutouts layered in front of the background.
Both James Cameron and Michael Bay have spoken out against converting 2D films to 3D, saying that the to-date dismal results of the conversion process could kill off audience interest in 3D. However, there's no sign that the industry is paying much attention to their cautions. In fact, there are plans to convert the entire Star Wars series to 3D for reissue, as well as a host of other films and even television shows.
It reminds me of Ted Turner's efforts years ago to colorize a library of black and white films he had acquired from MGM and Warner Bros. Turner faced blistering criticism but pressed on, saying that there was no market for black and white films on television or home video. However, his own Turner Classic Movies, as well as TV Land and other cable channels, showed that there was still a big audience for black and white movies and television shows.
The 2D to 3D craze reminds me a lot of colorization: It's expensive, it doesn't work very well, and lots of people are complaining about it. It's likely that 2D to 3D is also going to have much the same life as colorization. Within a year or two, producers and distributors will realize that conversion isn't the way to go, and that 2D isn't so bad after all.