Google is now seeing more than 850,000 new Android device activations per day, and Android head Andy Rubin says the search giant will “double down” on Android tablets this year.

But the real key to Android’s success could be found in Google’s acquisition of Motorola Mobility, which was recently approved by EU and US regulators.

The reason for that is simple: to win in the software world, it helps to win in the hardware world, and to win in the hardware world, it helps to win in the software world.

Case in point: Apple. The iPad wouldn’t have been successful without iTunes, iOS wouldn’t be what it is today without the iPhone and iPad, and so on and so forth.

As Daring Fireballs’ Jon Gruber succinctly put it recently, “Apple is an experience company. That they create both hardware and software is part of creating the entire product experience.” He points to an Alan Kay quote that Steve Jobs was apparently fond of:

People who are really serious about software should make their own hardware.

Google, of course, is serious about software, and in particular, its Android OS. But it’s obviously hasn’t been anywhere near as adept when it comes to hardware. The company’s acquisition of Motorola Mobility could change that, but it might not because of political reasons.

As reported by The Verge’s Nilay Patel, Google is building a “firewall” between its Android team and its new Motorola Mobility subsidiary:

Rubin said he was “painfully aware” of concerns, but stressed that Google has “literally built a firewall” between the Android team and Motorola. “I don’t even know anything about their products, I haven’t seen anything,” he said. “They’re going to continue building Motorola branded devices and it’s going to be the same team doing it.”

Such a comment is probably designed to appease Android partners that compete with Motorola Mobility, many of whom were, for obvious reasons, not exactly thrilled when their OS supplier announced it was buying a competitor that makes devices. But such a comment also suggests that Google is going to struggle to take advantage of its new asset.

To really heat up the battle with Apple and iOS, Google would want its Android team working closely with the folks at Motorola Mobility. Letting the people designing the software work side-by-side with the people designing phones would put Google in an Apple-like position, and even if there’s only one Apple, there’s little reason to doubt that Google could have used such a relationship to address some of the issues that plague the Android ecosystem.

Instead, Google has sort of painted itself into a corner with its Android distribution model, and while that doesn’t mean its acquisition of Motorola Mobility won’t bear fruit, it almost certainly won’t bear as much as it could have under more ideal circumstances. That’s bad news for Google, and good news for Apple.