As it has been with PCs, the more complex a machine becomes the more prone it is to abuse. Such is the case, apparently, with smartphones, particularly those capable of running programs we formerly thought of as existing solely on computers, like web browsers, instant messaging programs, et cetera – and viruses. Cell phone viruses have been very rare to date and limited in their scope. Analysts are concerned, though, and claim that in the near future we could see a large rise in the number of cell phones becoming infected by bots.
The danger is pretty clear. An infected cell phone is a mobile, typically always-on device. While Internet-connected ones often have a limited amount of bandwidth available, if you had millions infected it could add up to cell phone botnets becoming a problem. For the end user, it's even more of a problem than it is for those who become victim of botnet attacks. Not only would it be hard to tell if your phone was infected, but odds are the phone company would be more than willing to pass massive charges for data consumption on to you.