[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.