I don't know if its badly tuned sets, but I have watched 3D on some demo sets at Costco and the picture has the 3D effect in the foreground, but the background looked so flat it was disturbing. I have seen much better pictures on good HD sets.
I have a feeling that the active 3D shutter glasses are not charged in most of those demo units. Costco is a horrible enough environment to demo TVs as it is (bright flood lights, most of the TVs mounted or displayed at heights that cause noticeable color shifting with LCD sets, most of the TVs set to overly bright and sharp factor defaults, etc.).
The 3D demos require more attention to detail (i.e., keep the glasses charged, keep them clean, setup the demo at the correct distances, and make sure that the viewing is at a straight on angle. They frankly don't care if the TVs are correctly setup. Those 3D displays probably worked right the first day, and then they just ignored it afterwards. At least, the Best Buy stores in my area keep the glasses charged and take reasonable care of their 3D demo units.