One of the topics I wanted to cover in my series on online advertising was Online Ad Exchanges. Well, Robert Guth and Kevin Delaney at the Wall Street Journal have beaten me to it with a great article today. The article provides a great overview of how the exchanges work.

Also, I have to give myself a little credit … I predicted on April 4th a Google / Yahoo / Microsoft showdown on Read/WriteWeb. Currently, the first two parts have come true with Double Click’s planned exchange and Right Media’s exchange currently being housed at Google and Yahoo respectively. According to today’s Wall Street Journal, the third piece will emerge soon with Microsoft currently making a build versus buy decision.

Meanwhile, Microsoft has started developing a prototype of an exchange and has also considered buying one of the start-ups, say people familiar with the company. Microsoft General Manager Joe Doran declined to give details but said Microsoft has been studying the exchange model and “what it would take to build an exchange.” But, he said, “it’s still very early for the exchange concept to really catch on and drive to large scale.”