Interesting stuff. I think the autism angle is, if anything, a little overanalysed though - filters exist because actually, it's not an artificial construct upon how socialising works. That's how everyone works - that's why you have so-called "best" friends, then others farther outside your circle of trust, etc. Rating friends to a degree helps with that, especially if such ratings (on systems like Livejournal and Facebook) allow content to be restricted amongst only a certain restricted cabal.
In a lot of ways, saying that all these social networking sites make interaction a bit autistic is true though. Not in the way the author intends, however - it's just that when you're dealing in pure text, a literal interpretation and the lack of other social cues mean that interaction is less tiring for us, and more true to the way we think. It's just straight text and ideas, none of that complicated body language facial expression stuff. That this comes naturally for us, and others have to also conform to it (since, before Second Life, it was the only game in town), of course the interaction is a bit autistic on a certain level. That's just the nature of the beast. But the other criticisms are, I think, outright wrong.
On the flipside, the stuff I hate about Facebook, MySpace and their ilk are the way that skinning, music, stupid quizzes and other asinine crap that requires little or no thought seem to have come to dominate. I guess that's what the mass-market wants, in some way. Easy, trend-following plug-ins, but it irritates the hell out of me (one of the reasons I mostly stick with Livejournal - it's all about the text and your thoughts. LJ has evolved, as the author says, but it's evolved to be mostly used by a pretty intellectual subset of internet users).
I had a train of thought when I started writing this, but it seems to have run off the proverbial rails.
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"You're never more alone than when you're alone in a crowd"
-Captain Sheridan, Babylon 5
Music of the Moment: Radiohead - In Rainbows