Why are 3D numbers falling?

"Toy Story 3" did very, very well at the box office in its opening weekend, but only 60 percent of the gross came from 3D screens. That's lower than the openings for "Alice in Wonderland" (71 percent), "How to Train Your Dragon" (68 percent), and "Shrek" (62 percent). The percentage decline could simply reflect the limited number of of 3D screens - "Toy Story" has had to share the stage with "Shrek." From Variety:

"Toy 3" occupied 2,463 digital 3D screens; while in its fifth frame, "Shrek" held on to 1,300 3D screens. As of last month, the U.S. 3D screen count stood at 4,384 and approximately 2,500 3D locations.

There's bound to be speculation - founded or otherwise - that the lower numbers point to a 3D fatigue among moviegoers. Seems early for that to be happening, but with more 3D features due out this summer, it's possible there will be pushback, especially for the less-heralded fare. Hollywood types are closely monitoring 3D results because it's a potentially huge revenue source.