Rough Type has interesting comments on patterns of web traffic and patterns of economic rewards for the traffic. His conclusion:

What's being concentrated, in other words, is not content but the economic value of content. MySpace, Facebook, and many other businesses have realized that they can give away the tools of production but maintain ownership over the resulting products. One of the fundamental economic characteristics of Web 2.0 is the distribution of production into the hands of the many and the concentration of the economic rewards into the hands of the few. It's a sharecropping system, but the sharecroppers are generally happy because their interest lies in self-expression or socializing, not in making money, and, besides, the economic value of each of their individual contributions is trivial. It's only by aggregating those contributions on a massive scale - on a web scale - that the business becomes lucrative. To put it a different way, the sharecroppers operate happily in an attention economy while their overseers operate happily in a cash economy. In this view, the attention economy does not operate separately from the cash economy; it's simply a means of creating cheap inputs for the cash economy.

It strikes me that this dynamic, which I don't think we've ever seen before, at least not on this scale, is the most interesting, and unsettling, economic phenomenon the Internet has produced.

The comments are interesting, too.

My guess is that increasing chunks of the economic value will get eaten up in the competition to attract the free content, so the overall returns may not be that high to the sector. And that the favored sites will shift periodically, with none reigning for long.