Earlier quoted context omitted.
OpenX Enterprise is definitely being pushed hard. They also continue to work on OpenX Market, their exchange. OpenX is not good, but yeah a good number of people are using them.
I'm not surprised that many people use OpenX -- I'm surprised at how little competition there is for ad servers. Last year I wanted to build an ad server that could integrate with legacy backend systems and add some custom targeting logic, but I couldn't figure out a good way to do it. All the popular ad servers are either crappy, too limited, too expensive, or some combinaton of the three.
Re: Microsoft Writing Off Nearly All of the $6.3 Billion it Paid For aQuantive
#51http://www.adzerk.com/ seems to be the only real upstart in the game, as far as I can tell.