Interesting point... and you bring up a whole new wrinkle in the equation: People are having meetups, and that can really jump start organic interaction; it's one of the "good" things from Facebook-- people there DO know a lot of the people on their friends list "personally," as a result of which it becomes harder to "fake" interaction.
Occasionally, it's difficult. For example, I have somewhat over 3,600 followers... there is absolutely no way on Earth I could possibly hope to check them all out, and still have time to sleep for the next four weeks. I can barely keep up with 1/7th as many (about 500) that I follow.
So comments become really important. I might not follow someone (and that doesn't mean I don't "value" them), but if I see their name regularly it's a good bet it'll turn into a spontaneous return visit to their content. But still, many days are like this one: I have already left about 30 comments today, and only TWO of those were on someone else's top level posts.