1. Finding 3D content
3D TV's lack of mainstream adoption means fewer 3D broadcasts than to regular ones. So owners of 3D TV sets are only getting access to a small number of 3D shows in return for their purchase. It's the chicken and egg story all over again; more 3D broadcasts will probably only follow when more consumers buy 3D TV sets...but of course consumers only want to buy into 3D when they see more 3D shows appearing in the TV guide!
Apart from 3D TV, the other significant 3D content platform is Nintendo's 3DS. This handheld games console recently received an $80 price cut, presumably for missing Nintendo's sales expectations. The 3DS has sold a lot of units however and there are plenty of 3D titles available...
2. The 3D experience
...unfortunately however many people have experienced headaches and nausea when using the Nintendo 3DS. The 3D effect on the Nintendo 3DS can actually be dialled down and completely turned off, although this obviously 
negates a the headline feature. It didn't help matters when Nintendo itself seemed concerned about children under 6 years of age using the 3D feature of the 3DS.
People sometimes also report experiencing headaches or nausea when watching 3D TV, and this problem has continued to hold back many from buying these sets. After all, watching TV should be about relaxing, not about needing to go for a lie down afterwards!
Some of the newer technologies are moving towards glasses-free 3D, wherein the 3D effect works as long as the viewer is standing in a specific place relative to the screen. I saw several of these sets at CES this year, but unfortunately many people around me weren't able to perceive the effect without using glasses.
However glasses-free technology definitely makes more sense from a consumer's perspective, especially if you already wear glasses. Putting 3D glasses on top of regular glasses is an inconvenience. These sets are not widely available as a mass market option just yet.
3. The cost of 3D
So with a lack of content and a sub-optimal viewing experience in many cases, one might expect stores to be selling off 3D TV sets for cheap to reel in consumers.
That's certainly been Nintendo's approach in cutting the prie of the 3DS so significantly. But sadly most 3D TVs still cost significantly more than most regular HD TVs and the glasses are expensive, often costing around $150 per pair.
The costs quickly add up for a family wanting to buy glasses for everyone, and hosting a 3D Superbowl party quickly becomes prohibitive because friends can't always bring their glasses towatch your 3D TV set. We're still waiting for a 3D glasses standard to become adopted across the industry, so glasses for one manufacturer's 3D TV would be certain to work with another manufacturer's set.
