Since the dawn of time, BlackBerry smartphones have been the mobile communicator of choice for the United States federal government. The federal National Institute of Standards and Technology has been approving hardware and software to meet the FIPS (Federal Information Processing Standard) since 1995, and today iOS 6.0 was granted FIPS 140-2 certification. Specifically, the iOS CryptoCore Kernel Module 3.0 was assured to to meet the security requirements of the government.
Now having FIPS certification means that both the iPhone and iPad can be used in federal agency applications and as well as in private enterprises that access those networks. It's worth noting that FIPS certification doesn't apply to the military - the Defense Information Systems Agency is working to certify iOS 6.0 on their own security standards. Though it is likely that iOS 6.0 will get that approval soon.
The slowness in getting BlackBerry 10 to market proved to be detrimental to their previously all-but-guaranteed business with government agencies. With Apple and Samsung having already conquered the consumer market, they've turned their attentions towards lucrative government contract business. While BlackBerry 10 has had FIPS certification for a while and recently received Department of Defense DISA approval, they're already looking at competition from the approval of Samsung's Knox software just a few days ago. iOS 6.0 reportedly isn't far behind.
Personally, I've been a member of the Ohio Army National Guard for nearly a decade, and during that time has witnessed mounting frustration with the aging fleet of BlackBerry devices currently deployed and the back-end services supporting them. Demand for modern handsets - specifically those running Android or iOS - has been running high for some time from the employees of the DoD. It's only going to be a matter of time before they start finding their way into the hands of federal government employees across America.