So we keep in touch with these people we would ordinarily have forgotten about, or perhaps had an occasional thought about but not cared enough to pursue. Is this change encouraging a meaningful relationship, or just a superficial one?
Deleted my FB account once I had the realization above. People I speak to regularly, I speak to regularly regardless. Not surprisingly, none of the 'long lost' contacts I picked up have kept in touch with me since then; nor have I attempted to keep in touch with them.
Which just serves to reinforce my point - when it was no longer convenient, we stopped keeping in touch. Which means that neither party actually cared enough to pursue it.
Social media makes it easier to avoid and mitigate that awkwardness. The obvious response is, "That awkwardness shouldn't matter," but "should" is a big word. It still matters.
False dichotomy. Friendships come on a continuum. If facebook shifts some of the marginal ones over the line from "not worth maintaining" to "worth maintaining", surely that's a good thing.
One day I saw on facebook that an old acquaintance was looking for company at an interesting-sounding dinner. So we went there and had a good evening. We've been in very little contact before or since, and would probably not have been in touch at all without facebook - but that was a nice evening nevertheless, and well worth having facebook for.
Friendship doesn't need to be a black-and-white concept; there are close friends and there are distant friends.
How many close friends do you think your grandparents had? How many people did they interact with? This is not a byproduct of passivity, but a byproduct of having a larger pool of "friends."