I think this article kind of misses the point. Sure, social network websites as distinct businesses are dying off — I’m surprised anybody thought they’d make money doing it to begin with. It’s like selling ice in the Arctic.
The phenomenon of Social Networking isn’t dying — it’s thriving. It’s just that the whole Internet is a social network.
Once people start realizing that, and the tools for connecting people outside of proprietary “sites” have become more useful and widespread, then there’s just no need for “social networking sites” like Friendster.
The only kind that will survive are specialty sites, like dating/matchmaking services or ones where people already share something like a career discipline or hobby.
Otherwise, the Internet already links everybody.
It does make the astute observation, though, that the problem with a lot of artificial social network sites is that they don’t have anything happening once you get there. That’s why things like LiveJournal (which I’ve basically given up on, but it’s still growing like mad) and RSS aggregators linking people’s blogs are thriving.
Social networks as a money-making business plan are, though, mostly kaput.