This is not a bubble, a bubble is when any idea no matter how stupid or how long the sunshine laden plan will take to break even, gets funded. I think there is an "we will make money off of ads" bubble, but that it localized to a segment of the web.

I would say an expertise of mine is analyzing bubbles. Web 2.0 definitely has a ton of funding in companies that are moving further down the quality chain. Also, the supply of investment is absolutely a sign to watch.

With that said, bubbles can last years.