Kindle Fire generating “hundreds of millions” of monthly ad impressions

Amazon (s amzn) has finally provided a glimpse of overall Kindle sales, but it’s still not quite clear how much momentum Kindle Fire, Amazon’s breakout tablet, really has. Well, mobile ad network Millennial Media is providing another solid bit of data, saying that Fire ad impressions on its network have been growing by 19 percent daily in the first few weeks after its mid-November launch.

According to Millennial Media’s November numbers, the Kindle Fire’s impression growth is now on a faster initial pace than that of the Apple iPad, (s aapl) though it has the advantage of selling into a more mature tablet market and comes with a much more affordable $199 price tag. The fast start of the Kindle Fire has helped push Millennial’s “connected devices” category up to 16 percent of all impressions, up from 14 percent in October.

“We’re not just seeing millions of impressions, we’re seeing a monthly run rate of hundreds of millions of impressions” for the Kinde Fire, said Millennial Media.

Amazon’s tablet has helped Android (s goog) secure 50 percent of all ad impressions, but that’s a noticeable slide from the 56 percent it held in October. One key difference appears to be the launch of Apple’s iPhone 4S, which boosted iOS’ share from 28 percent in October to 30 percent in November. RIM (s rimm) also had a big jump in November, with its share of impressions growing from 13 percent in October to 17 percent in November. That seems like a big leap for RIM, which does have new BlackBerry 7 devices selling but hasn’t appeared to be outpacing Android or iOS in sales.

Apple increased its lead as the top device manufacturer on Millennial’s network with 25.7 percent of impressions, up from 23.5 percent in October. Samsung reclaimed the second spot with 17.5 percent of impressions, while HTC dropped to fourth behind RIM. The iPhone also lengthened its lead on the competition in November with a 13.5 percent share, up 8 percent from 12.5 percent in October.

The numbers highlight the growing oomph behind the Kindle Fire, which, despite some so-so reviews, has been selling extremely well. Amazon said last week it is selling more than 1 million Kindle devices — e-readers and tablets — a week, and the Fire has been the best-selling device and most gifted product on since it was introduced.

It’s logical that the Fire is counted by Millennial as an Android device, because it is built atop Android. But as we have noted, the Fire is becoming its own platform as well, with its own set of development demands for developers. For the time being, Android’s share is benefitting from the Fire, which now leads the pack of tablets based on Android. But over time, it could be its own branch of Android that leads people away from Google’s base platform.

Millennial’s numbers also show that Apple is getting a pop from the iPhone 4S and is able to claw back some impressions from Android. These two OSes are still well ahead of the competition.