The release of the Motorola Droid, a much-anticipated device running Google Inc.'s (GOOG) open-source operating system, Android, is less than two weeks away, and the blogosphere is alive with speculation that this could be the Next Big Thing in mobile devices, possibly even supplanting the iPhone as the Device to Have (and give away) for the upcoming holiday season.

That isn’t going to happen, for reasons that go beyond Motorola’s dismal record of recent handset devices. The Droid may be a perfectly fine smartphone – the early reviews are solid, if not ecstatic – but, as TechCrunch tech blogger MG Siegler points out in this entertaining post, those who think that Android will compete with the iPhone are confusing two very different types of mobile devices and systems.

“In a religious sense, the iPhone is a monotheistic religion. Basically, its OS believes in one device,” wrote Siegler. “Meanwhile, Android, Windows Mobile, BlackBerry, Symbian, etc. are all polytheists.”

In other words, all those other operating systems run many different kinds of devices (although I’d place BlackBerry in the “monotheist” camp, since all its devices are simply BlackBerry variations). There are larger problems, of course: A new big red flashing warning sign about smartphone security appears on one of the major tech news sites daily. The more fundamental problem, though, is also Android’s strength: It’s an open source OS being adapted by handset manufacturers for a range of devices. As such it will not initially have, and may never have, the fully integrated voice-and-messaging power and reliability of the iPhone or BlackBerry ecosystems.

Though Apple (AAPL) has had its own red-faced moment recently, the snafus with both Gmail and Google Voice in recent months underline this point. Android will no doubt be a terrific system for consumers who are more casual about security and about integrating their voice and messaging capabilities. But its reliance on Google Voice makes it hard to imagine Android-based devices as the primary tools for professionals, much less for business IT departments.

Google, which specializes in “permanent beta” applications, is not exactly known for its SLAs and backup options. And TechCrunch founder Michael Arrington reported that he’s hearing rumblings from the developer community that the proliferation of Android-based devices – handsets from Motorola Inc. (MOT), Samsung, HTC, and LG (1577.TWO) are all due before the end of the year – is making it difficult to write apps that cover the full spectrum.

Seventy-five million phones running Android will be sold in 2012, according to research firm Gartner. That will make it the second-most prevalent mobile OS in the world, and the wide spread of an open-source mobile OS is a wonderful development. But Google still has a few bugs to work out.