Android's march towards smartphone market dominance continued on Tuesday, as Google's Android chief Andy Rubin disclosed that activations continued to grow at a torrid pace. "There are now over 500,000 Android devices activated every day, and it's growing at 4.4% [week over week]," he tweeted early Tuesday morning.

Putting that in perspective, it was only at the Google I/O conference in May that Google reported surpassing 400,000 daily activations. Before that, in December Android surpassed 300,000 activations per day, and at that point was the first time it was surpassing total iOS daily activations on a regular basis.

Furthermore, if Android is able to maintain such a rapid growth rate, its daily activations could surpass one million devices per day by the fall. That's likely not to occur however, as the smartphone market is not big enough yet to support such a high sell-through.

It may be eventually though: Gartner predicts that Android will ship some 315 million devices in 2012, giving it half of the market, and very close to that million-per-day activation rate.

Google's successes in just the smartphone sector with Android is now allowing it to claim the title (at least for now) of largest mobile operating system. Apple had been using some accounting tricks -- much to the chagrin of Android fans -- which when combining iPad, iPod touch, and iPhone sales and activations together, still gave it the overall lead.

With Android now activating over a half-million units per day, that trick will no longer work. As of last count, about 325,000 iOS devices were being activated daily.