The term "social TV" has been thrown around a lot these days to describe any and all second screen experiences created around television shows.
But it's well worth noting that many of these apps and features have nothing inherently "social" about them: they are information sources that viewers may choose to share on social networks, but that is not the primary function.
I'm talking about apps that provide statistics during football games or episode guides during dramas and cast bios during reality shows.
That type of functionality is going to be more valuable to many viewers than something that allows them to have conversations during the show. It's well suited for family viewing-- only 31% of Americans watch TV alone -- where we are more likely to share whatever we've learned with the other people in the room (as opposed to say, the entire Twitterverse.)
It is also key insofar as creating any kind of buzz: the more content you give to people to help expand their knowledge of the program, the more likely they are to share that information at some point, both online and off.
That's why the quality of the second screen content and how much buzz it helps create is going to factor in to how successful a show is. Content that adds to the viewer's experience is far more valuable than a few random pictures of cast members or even the ability to read a Twitter feed.