Emails are flying out of Redmond with this speculation: Microsoft CEO Steve Ballmer's botched $50 billion bid for Yahoo could mean the end of his career. While Microsoft's board reportedly gave the CEO considerable leeway in handling the deal, his dithering approach and his failure to sell the deal both to Yahoo's board and Microsoft's own executives don't reflect well on the sweaty screamer. The only problem: Microsoft has no obvious successor for Ballmer.