If I have any social networking anxiety, it's not about friend count. It's anxiety over wasting my life catering to wannabe web personalities trying to build a following via attention-whoring or wasting precious moments of my life scrolling through every mundane update every idiot on my list posts when their new baby farts (or, worse, the ultra sound images and the nine months of constant uninteresting updates that f…
I was resistant to facebook at first, but I've found it a great way to keep in touch. Yes, sometimes people over-share, and sometimes there is a temptation to over-share yourself. But if you're an adult, it's easy to recognize that and make allowances for that in other people. It's part of the human social fabric.
And it's quite useful to be able to post vacation photos (as one example), or blast out an update and have group comments -- it seems less isolating, and frankly less annoying, than group email updates when your friends are geographically separated.
Do people "collect" friends? Yes... that can happen. But like anything else, you can use it like an adult, and play to it's advantages, rather than it's disadvantages.
To some geeks, uninitiated social contact that doesn't make their own special needs primary is an annoyance. But -- trust me, the resulting anger and isolation isn't really worth the curmudgeon act. You are not that busy, you're are probably not solving world hunger, etc... lay off the snobbery.
Now Twitter on the other hand, is a little different. Its nature is to be more of a public platform. Something public personalities use -- and in that case, the character limit makes something that should be deeper, much too shallow. I use it as a headline news ticker ('cause the existing RSS tickers are less capable than twitter clients), but don't bother following individuals.