Not to be left out of the ad exchange party, Microsoft plans to acquire AdECN, an online ad exchange similar to Right Media ( acquired by Yahoo) and DoubleClick’s (soon to be acquired by Google).
The idea of an ad exchange is similar to a stock exchange, where buyers and sellers work through a broker. Similarly, AdECN does not do business directly with advertisers or publishers; it works instead with ad networks, ad brokers, and a few ad agencies that maintain relationships with buyers and sellers, acting as a network themselves.
If you’re keeping score, that leaves newcomer ContextWeb and its ADSDAQ exchange as the last independent player standing in the ad exchange space.