Yes, buying the highest end computer every year IS stupid if you can't afford it. Just like every year buying the Mustang of the year.
But, for those who can afford it, go for it. I personnaly know people who can't stand the idea of driving the same car two years in a row. Like I know some people who couldn't be caugh dead with last year's computer. But they can afford it, so whatever, do what you want with your money.
But for real, hardly anybody needs to change their computer every year. A computer is not outdated before at least 2 or 3 years. I'd say 2 years for hard core gaming and 3 years for the latest applications.
My home computer is a Celron 333 (about 4 years old) and it gets the job done. I run all the latest software (Windows XP, Photoshop 7, Flash MX, Dreamweaver MX, yada yada yada) perfectly fine. Of course, it's slower than my computer at work (1.4 Ghz), and I wish I could have something faster. But really, I don't see it being worth 2,000$. I do all the same work, run all the same programs. To save 2,000$, yes, I will wait an extra 10 seconds for Photoshop to open. The way I figure it, I can probably get this computer to last another year, then I'll buy me a new one. Depends on the money issue. But I need a new car before that (a 10 years old Ford Escort).