Hackers hack Symbian
According to the most recent McAfee Threats Report: First Quarter 2011 (PDF), it looks like that when hackers target mobile devices they target Symbian devices much more frequently than they target other devices. Here's the graph from this report that shows the relative frequency of malware for various mobile platforms:
I don't have a protractor handy so I can't measure the sizes of the pieces of that pie chart, but it looks to me that a bit over 75 percent of all mobile malware targets Symbian platforms. Maybe I just haven't been paying enough attention to hacks of mobile devices, but I was surprised to see such a big fraction of malware targeting Symbian devices.