The title seems to imply the content of the post is incorrect because of the Alexa numbers, but the Alexa numbers are not really relied upon as a strong premise. (Actually, there isn't really a strong premise, he just sort of asserts his opinion)

Anyway, that doesn't mean he's totally wrong either. Although I admit there is still space in the "long tail" for more new web apps, it will be difficult to keep making web apps once every site has to battle existing players. Google/Yahoo/Microsoft/Cisco won't prop up the industry with constant acquisitions of unprofitable companies forever.

Whaddayaknow, maybe Alexa is the problem! Compete.com shows exactly the opposite trends with increasing 2007 traffic to all the 2.0 sites mentioned. (http://snapshot.compete.com/techcrunch.com+technorati.com+gigaom.com+)

Is there any consensus on which of these sites (Alexa or Compete) is more reliable? Or at least...less unreliable?

I don't know much about Compete, but Alexa stinks. It's a small, self-selected group of users that in no way represents the Internet at large.

I'm not the only one who thinks so: http://franticindustries.com/blog/2006/12/18/why-alexa-sucks/

I've had questionable trends from either one. I can't say which I find more consistently reliable, but it'd probably be on a case-by-case basis on whichever results are skewed in my favor. ;)

Valleywag wrote about how he was fooled by bad Alexa data:

http://news.ycombinator.com/comments?id=5233