Medical students often need to get some type of PDA for their clinical clerkships. They may be required to enter patient information or log their procedures. Also, since they're often asked to write prescriptions (not sign them, just write them), they need to know how to look up drug dosing. Software like Epocrates can be very helpful when you're filling out 15 scripts on different medications. Gone are the days of flipping through a huge PDR to look up dosing.
So how does the BlackBerry fit into all of this? Traditionally, Palm had the greatest marketshare in the medical field. Recently, the Apple iPhone has become very popular among medical students, residents, fellows, and attendings. Yet you still find some medical students who are in their early years of training who are attracted to the BlackBerry. Why? Part of the reason could be that they may have come from a corporate background. Others may be serious "texters" and they may have gravitated to the BlackBerry because of the excellent keyboard and texting capabilities. For others, it's simply about cost. You can get a free BlackBerry from many carriers.
I've been wondering why RIM hasn't been more aggressive with their marketing towards medical professionals. They should partner with more software developers and have more available for their devices. Otherwise, they'll be left in the dust with the Apple iPhone and the Microsoft Windows Phone running off into the sunset.