What does 2012 have in store for Android, Windows Phone, BlackBerry and iOS?

Research In Motion's (NASDAQ:RIMM) decision last month to replace long-time co-CEOs Jim Balsillie and Mike Lazaridis with COO Thorsten Heins crystallized the challenges that remain for the BlackBerry maker. The company must push back against declining market share in the U.S. market, deliver its BlackBerry 10 platform on time and with perfect execution and convince consumers, carriers and developers alike that RIM is a company worth betting on. One of RIM's staunchest U.S. allies, AT&T Mobility (NYSE:T), thinks RIM has a place at the smartphone table--but CMO David Christopher recently noted that RIM needs to "innovate quickly and execute." 

However, RIM isn't the only smartphone player facing serious issues in 2012, analysts said. Apple still needs to try to crack emerging markets and expand its presence in cloud services. Google will need to manage the integration of Motorola Mobility (NYSE:MMI) as well as the ongoing patent litigation affecting Android licensees. And Microsoft will have to continue to build enthusiasm among consumers for its widely praised platform, while at the same time maintaining interest among its licensees despite the fact that Nokia (NYSE:NOK) is its premier partner.

If that sounds like a tall order for each company, that's because it is. What follows is a primer on the pros and cons of each of the four major smartphone platforms as well as the key underlying challenges confronting them in 2012. (Even though Symbian retains a substantial global market share, its U.S. presence is negligible and its future is dim. So, the focus will be on iOS, Android, BlackBerry and Windows Phone.)

Will each platform be able to rise to the challenges it faces? Check out our special report on each of the world's main smartphone operating systems:

What does 2012 have in store for Android, Windows Phone, BlackBerry and iOS?