It's true that algorithmic traders from Wall Street will be let down when they come to RTB trading and see how simple and undeveloped the ad ecosystem is compared to financial services. Arbitrage is still important but not the driving force for advertisers' success. Reach is more important: being able to show ads to more of the users in your targeting segments.

Google made the Admeld move for reach. It's partially a "publisher relationships" play, certainly not the technology, but mostly just the easiest way to get a giant new chunk of RTB volume.

I thought this blog post summed it up well: "It's the QPS, Stupid" http://jaysears.com/2011/06/10/google-admeld-the-need-for-di...