I want you to think about your IRL friends for a second. Just your IRL friends. Adding your URL friends to this equation will muddle the results.
Nowadays, I'm sure that the number of your IRL friends who have a Facebook far outweigh the people you know who do not have a Facebook. With Twitter, at least in my experience, it's about 30/70, the 30 being IRL friends who have Twitter. As for friends who post on YouTube, the number gets even smaller. I have a few IRL friends who post videos on YouTube but I have more friends who have a Twitter account and even more friends who have a Facebook.
Well, since it makes sense self-marketing-wise, it's a pretty good chance that your IRL friends who post on YouTube also have a Twitter and a Facebook. Right off the bat, if you post content to all three, you're in the minority along with me.
If I think REALLY hard, I can only think of a handful of people I know who post to all three. And some of those who post on Twitter have it set up to post the same posting on their Facebook. What's the point, man?
Take into account Blogspot, Dailybooth, my other YouTube channels, my Tumblr, and I don't feel it's unfair to think that I post more content to the Interwebs than the average person. I even have a flavors.me account. I don't know why, but I do.
I originally planned to write a completely different sort of blog post but I needed to get all this out first. The second IRL URL blog is coming soon. :)