[wangwei]

I do agree with you. But if you view it this way, are't most systems cyclic? companies, economic boom and burst. Even America might fall one day after its peak. The important question is how long the cycle is. Previous social networks have never gained such mainstream adoption and user participation as Facebook have. Facebook might fall one day, but my bet is that it's gonna take longer than you anticipated. Everything is a fashion thing, essentially (even religions).

[jacquesm]

The interval between shifts seems to be lengthening, I think this is due to the increased effectiveness of the predominant social network du jour to exploit network effects. Maybe that alone will be enough to counter the 'fashion' factor but I don't think we're there yet.

And sure, everything is eventually cyclic (well, almost everything) but I mean cyclic on a measurable (say 10 years) time-scale, not something geological.