I've become mildly aware of de-friending and de-following on Facebook and Twitter, respectively.
As Twitter garners many non-acquaintance followers gained from either my industry-related or one-off culture comments, some amount of de-following on Twitter is kind of to be expected -- someone sees an interesting comment, clicks "follow" and then later realizes my stream ain't their cup of tea. I definitely notice people signing up for a little RJ, then having buyer's remorse and de-following me (usually within a day or two of following me in the first place).
On the other hand, my Facebook "friends" generally aren't strangers; I am usually personally connected to FB friends via actual live connections, either personal or professional. Yet despite actual personal connections, I still experience a fairly high rate of de-friending from FB friends, and I find this more interesting than losing a few non-acquaintances who happened to follow me on Twitter. And it's really interesting when I discover the de-friending friend is actually someone I've spent some significant time with (ouch)!!!
To be objective to both the Twitter and Facebook camps (unhappy campers, actually), I do happen to write what I like to think are thought-provoking tweets and status updates. I recognize that some of these comments may cross the line for some people; the statements might even offend some (even if my intent was merely provoking thought and conversation).
In all of these de-friend and de-follow instances, I try not to take them personally -- I don't (at least I think I don't). But I also have to face the possibility that perhaps my tweets and updates aren't thought-provoking-cum-offensive to some; rather, I may just be a big bore. Crap, maybe I'm just not popular. Oh no, I'm back in junior high again. Ugh...