http://scitech.blogs.cnn.com/2010/04/15/samsung-issues-warnings-about-3-d-tv/?hpt=T2

Samsung warns that excessive use of 3D-TVs can cause disorientation so severe, that one could fall off the couch. Also:

“Pregnant women, drunk people and “those who are sleep deprived” should not watch 3-D television because of potential health issues, electronics manufacturer Samsung says on its Web site.”

“Viewing in 3-D may cause disorientation for some viewers,” the warning says. “Accordingly, DO NOT place your TV television near open stairwells, cables, balconies, or other objects that can be tripped over, run into, knocked down, broken or fallen over.”