For so long, the thrill of Facebook was about reconnecting with people you thought you'd never see again. ("Oh, Little Miss Popular from high school! Did she end up really fat?" ... "Oh, that hot guy from calculus class. Is he married now?") And so on and so on. But now veteran Facebookers find themselves at an impasse: There's nobody left. Having reestablished ties with a few hundred friends from your past, you may be wracking your brain for additional lost acquaintances to "invite." When you find yourself trying to find and friend the janitor at your old middle school, you know it's become a problem.

Meanwhile, as your rediscovered friends update you about their everyday goings-on, they offer you a multiple opportunities to recall the reasons you lost contact with them in the first place. Examples: "Don" was always a nonsensical rambler back in college--and lo and behold, his rants take up half of your news feed now. "Heidi" always sucked up in English class, and she finds ample opportunity on Facebook to display her mindless sycophancy anew. No wonder you neglected to fulfill your yearbook promises to "stay in touch!" Facebook has recently started allowing users to "hide" their friends, and you may be inclined to "hide" almost all of them.

4. Having Too Many Friends Takes the Edge off Facebook Postings

The downside of racking up so many friends on Facebook is that it's no longer safe to speak honestly about your thoughts and feelings. "I hate my job" used to be safe. But now you're friends with your boss and your colleagues. "I'm still hung over from last night" was once legit, but now your younger cousin is on there, and she has always looked up to you. Most people would prefer R-rated status updates from their friends, to keep things interesting, but instead everyone is sinking into precautionary PG territory, and it's getting rather dull. (For more on this subject, see "How to Avoid Facebook and Twitter Disasters.)

You've also probably grown up quite a bit in the five-plus years since Facebook began, in which case you aren't the same person who created your original profile and started writing on people's walls. Unfortunately, deleting all of that history is a big pain. You get a new boyfriend and have to wipe out all the photo albums of the old one. You get a new job and have to go scour your profile for inappropriate comments before friending your new colleagues. Reinventing yourself is hard with a wall full of history memorializing your past.