Corporate users have long been a stronghold for BlackBerry Ltd. (NASDAQ:BBRY), in large part due to its ironclad security. But Apple Inc. (NASDAQ:APPL) is making inroads and just picked up another huge customer, Ford Motor Company (NYSE:F).

Ford, the second-largest U.S. automaker, said it plans to replace more than 3,300 BlackBerrys with Apple's iPhones by year's-end.  A company spokeswoman told Bloomberg  that another 6,000 employees will be switched to iPhones over the next two years. The company plans to eventually provide iPhones for all of its 181,000 employees worldwide.

“It meets the overall needs of the employees because it is able to serve both our business needs in a secure way and the needs we have in our personal lives with a single device,” Sara Tatchio, a Ford spokeswoman, said.

Apple products are ubiquitous to the everyday consumer -- at home, on the train or the bus, clutched tightly in the hands of distracted users walking down any Main Street. But now the Cupertino, California, company is seeking to attract more corporate users, once the mainstay of Canada's BlackBerry, so the Ford deal is a big win. And it would seem to tie in nicely with its recent collaboration with International Business Machines Corp. (NYSE:IBM) to develop enterprise software for the iPhone and iPad.

The Ford deal with Apple is another blow to BlackBerry and its CEO, John Chen, who is trying to turn his company around by betting largely on software-based services for corporations, long its bread and butter. As a result, BlackBerry has fallen behind rivals Apple and Google Inc. (GOOGL) in the race to offer ever-more fancy smartphone features and third-party apps. Google's Android platform powers Samsung's dominant Galaxy lineup, and neither Apple nor Samsung have made any pretenses in the past about deftly courting consumers, not corporate.

At a company-sponsored conference in New York Tuesday, BlackBerry executives said that Apple and Google's Android-powered devices don't provide the same levels of security as its own BlackBerrys, absolutely paramount for the corporate sector.

Despite a host of challenges facing BlackBerry, the company still maintains favor with some corporate clients, law firms, and even the president of the United States.  New York law firm Skadden, Arps, Slate, Meagher and Flom said it relies on more than 1,000 BlackBerrys because they help ease the confidential, compliance process required by the firm's corporate clients. “There is not another manufacturer or developer that has achieved this level of security,” Peter Lesser, Skadden’s director of global technology, said, according to PC World.

And then there's Barack Obama -- the nation's president still uses a BlackBerry. He's banned from using Apple's iPhone for "security reasons" in an official capacity, but is allowed to use an iPad in a personal capacity.