Windows Phone and BlackBerry OS are headed for a knock-down fight over which has the smallest install base in the US, according to WMPowerUser. BlackBerry's share continues to plummet, according to StatCounter, as Windows Phone struggles to grow past its approximate 1 percent penetration. At this rate, the two will switch spots on the leaderboard during the last few weeks of 2012.

RIM has done nothing but lose the foothold it once had in the smartphone market in the last few years while Android and iOS have duked it out over positions one and two, respectively. StatCounter shows BlackBerry OS at just under six percent install base in the first week of 2012, and it sits just above three percent now; by early December, the OS is predicted to be on just one and a half percent of smartphones.

Microsoft and Nokia attempted to call down a nuclear strike to the smartphone marketplace with the high-profile release of the Nokia Lumia 900 in the US. But that nuke failed to launch, and Windows Phone's share stuck at around one percent.

Microsoft later announced that the Nokia Lumia line would never be upgraded to Windows Phone 8 from Windows 7.5, as we had suspected, sealing the phones' fate. Windows Phone sat at less than one percent at the beginning of the year, according to StatCounter, and is at roughly one and a quarter percent 28 weeks later.

Small though that uptick may be, it could be enough to overtake BlackBerry OS, if Windows Phone can maintain its paltry growth. Microsoft is set to release Windows Phone 8 this fall, likely along with a new range of handsets, meaning it could surpass BlackBerry's install base even sooner.