Once again, the CrackBerry has made an indelible mark on American society. Only this time, it's a good bet the marketing mavens at Research In Motion (NASDAQ:RIMM) are none too pleased. That's because, on Tuesday, the American Physical Therapy Association added "BlackBerry Thumb" to its list of recognized repetitive stress ailments.

Why's that so bad, you ask? First, because it's painful. According to the APTA, BlackBerry Thumb is caused by the unnatural use of the big digits in scribing email or playing games on smartphones like the BlackBerry.

And second, because the affliction isn't exclusive to the BlackBerry. The APTA says overuse of any smartphone or personal digital assistant -- from Palm's (NASDAQ:PALM) Treo to Motorola's (NYSE:MOT) Q to Nokia's (NYSE:NOK) E62 -- can cause BlackBerry Thumb.

Furthermore, the legal repercussions of BlackBerry Thumb are potentially serious for corporate users. Professor Gayle Porter, who teaches management at the Rutgers-Camden School of Business, has research that says employers could be responsible for employees who become addicted to mobile devices and subsequently acquire the malady.

Crazy, you say? Maybe it is. Fortunately, that's not the point to my article. This is: Research In Motion has lost all semblance of a competitive advantage. Look, I know it seems crude to say so when discussing a real and painful disorder but, seriously, if BlackBerry Thumb isn't all about the BlackBerry, then what is?

How about nothing? Everything that the BlackBerry can do, another device can do as well, thanks to mobile mail services from the likes of Visto and Good Technology. What's more, as once-proprietary devices such as the Treo have embraced Microsoft's (NASDAQ:MSFT) Windows Mobile, RIM has stood pat with its own incompatible system, just like Apple (NASDAQ:AAPL) in the 1980s.

We all know how well that worked out. Don't expect RIM to do any better.

Rest your thumbs and use your laptop to peruse related Foolishness:

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