ADOTAS – Google has restrained itself till this point, but as it begins running behaviorally targeted ads across its network of mobile applications, Big G is going to use device identification numbers to assist in tracking and targeting.

Because you can’t drop a cookie in an app, the device IDs are used to not only collect in-app behavioral data, but also to track conversions and enable frequency targeting. Behavioral targeting on the mobile web will still use good, old-fashioned cookies.

“Over time, we’ll be able to enable things like frequency capping, spam filtration, improved conversion measurement and serving ads based on topics of interest, all of which will help us display the most useful in-app ads; minimize the number of irrelevant in-app ads shown; and improve in-app advertising for users, advertisers and developers,” one of those mysterious Google spokespeople told GlickZ.

The device IDs will be given anonymous codes and Google promises that no personally identifiable information will be collected, but users can still opt out at the Android Market or in the Google Search app for iOS-powered devices.

While privacy advocates are likely to go nuts over this development, using mobile device IDs and device fingerprinting for behavioral targeting is becoming increasingly common — arguably such practices are more effective than cookies while keeping anonymous. Check out some of our conversations with Dave Norris of BlueCava for more insight into device fingerprinting.