Ballmer's 10th anniversary as CEO of Microsoft arrives in January, but it's hard to imagine he'll be celebrating. Microsoft stock has dropped by nearly 50 percent on his watch, lagging not just other tech companies but even the Dow Jones industrial average. Distracted by the Windows Vista fiasco, Ballmer has missed every big new tech market of the past decade. Google won the race for Internet search and keyword advertising. Apple won in MP3 players and online music sales, and now holds the high ground in mobile phones, while Windows Mobile fades away. Microsoft's Zune music player is a dud. Bing, Microsoft's search engine, will never catch Google. Ballmer is said to be a brilliant guy, but he got a black eye for the way he blundered and blustered and finally botched an attempted acquisition of Yahoo. He's a screamer and a bit of a bully--not the easiest guy to work for. If Microsoft were any other company, this guy would be in trouble. But the catch is, Ballmer was put into the job by Microsoft founder Bill Gates, and the two have been pals since their undergraduate days at Harvard. If Gates wants to get rid of Ballmer, he'll have to craft some kind of graceful exit that lets his buddy save face. Another problem: there's no heir apparent on the management team. Nevertheless, investors must be getting restless. Soon they'll start calling for a shake-up.