I see the same thing, but feel much more optimistic about it: it's not, in my mind, that tech is effectively fashion, but rather that there are "futurist" ideas that tech keeps trying and which keep not getting adoption, because it's not their time yet—the state of the art isn't there to make the experience for the average consumer (or the average developer) justify the costs.

An example of what I mean: the Apple Newton, and then 10 years later the Palm Pilot, and then 10 years later Windows CE and flip-phones supporting J2ME, and then 10 years later touchscreen phones and tablets. There have been four generations of "mobile app developers", but only the latest generation has seen any traction for their apps. This time the idea stuck; it will stay around, rather than coming around again.

If something like Paypal's prototype service (beaming money from one Palm Pilot to another) were set in this "revolution" of mobile instead of that one, it would be much more successful.