Wish I had more time now to review this:
Matt Stoller over at Open Left argues that this means that technoutopian libertarian dreams are dead and there is a necessary role for government.
Maybe. I have never read enough of the Long Tail arguments to have a Strong opinion, but I do want to point out that there maybe radical inequality in revenues between a Google or Facebook and other web services that aim to make a profit. In fact, a long tail is premised on that. But, the question was whether a business can survive in the long tail, as opposed to have equal revenues. If you have the head and not tail then you have an oligopoly which was never the merit of the long tail.
Finally, aggregators seem complicated. They get a little revenue from a massive volume of transactions, but if those transactions are distributed to a number of smaller players (ebay, Amazon marketplace, emusic, and so on), then you may have a viable market where one did not exist before- again, it is about viability, not equality.