With AdMob and Quattro Wireless off the market, the remaining independent ad networks are now left to woo the only major online player with serious aspirations in mobile. Make the deal appetizing to Microsoft.

The Federal Trade Commission?s approval May 21 of Google?s $750 million purchase of AdMob (see story), coming five months after Apple?s reported $270 million acquisition of Quattro, makes it easier for Microsoft to enter the mobile ad network market. But the House that Gates built has to move quickly.

Once Google integrates AdMob, it becomes a formidable player in serving ads across mobile sites and applications nationwide and overseas. Combined, both companies will account for one out of five mobile ads served in the domestic market.

Apple?s strategy with Quattro has morphed into iAd, its own ad network with expectations of being mobile?s Garden of Eden where everything is perfection and residents expected to play by the rules of the Lord.

Where does that leave Microsoft? The company is heavily invested in mobile advertising and search, as well as its Windows 7 operating system. Mr. Gates has gone on television several times espousing mobile?s role in today?s society and business environment.

So the vision at Microsoft is evident. Now all that needs to happen is speedy decision-making that realizes one reality: the mobile ad space cannot become a duopoly between Apple and Google.

Two?s a company, three?s a crowd
While other mobile ad networks do offer competition ? Millennial Media, the largest independent; Jumptap; and Yahoo, among others ? Microsoft is in a unique position to leverage its online clout across mobile.

Pairing itself with one of the independents mentioned above would clearly elevate Microsoft?s standing in the mobile world. It would also offer brands and agencies options other than Apple and Google ? whose differing philosophies still arrive at similar conclusions: platform dominance.

It will be interesting to see the cooperation between Google and Apple as the former places ads on the latter?s network and what defenses each have against Trojan Horses.

Microsoft may thank both Google and Apple for opening the doors for a quiet acquisition in the mobile ad space. After all, the FTC approved the AdMob purchase because it said Apple?s acquisition of Quattro provided enough competition. So why not one more hat in the ring, thrown by Microsoft?

Three strong cross-channel players in the mobile ad network market, along with a couple of spunky independents, should make for more market-friendly ad rates and technology for advertisers and ad agencies.  

A stool is stable with only three legs. Two legs make a ladder. Microsoft shouldn?t make it that easy for Apple and Google.