BlackBerry hit the market, RIM is celebrating a major milestone: 50 million units sold, with 21 million subscribers (suggesting subscribers have averaged over two BlackBerry purchases) transferring some three petabytes a month. That 50 million figure sounds epic -- and indeed, it is -- but let's take a moment to put it in perspective, shall we? Symbian found its way onto nearly 80 million handsets in 2007 alone, and the operating system (in its various forms, but mainly S60) is found on a quarter billion phones today. Windows Mobile, meanwhile, racked up 20 million units just last year. So yes, RIM should be proud of its accomplishment -- but if they're looking to get a little piece of Waterloo into the hands of every man, woman, and child on the face of the Earth, they've got a while to go yet.