Others were quick to say that they only use social features with real friends and family. I'm not sure why that would be a "but..."; it's the whole point of those features.
About 17% of respondents here said Yes. That's much lower. I have a couple of guesses why: first, a lot of commenters didn't seem to consider features like a game profile, friends list, or the activity feed "social features".
Interesting results! I don't have great data on this, but the XBox game culture report says about 1/2 of respondents play online multiplayer games. I think you have to have the social features turned on to do that, so I'm going to guess about 50% of XBox users have those features turned on.