Sources close to Microsoft say the company's bankers have begun signaling to Facebook CEO Mark Zuckerberg interest in acquiring his company. "We just want to gauge their interest, more than any real effort," one source told Kara Swisher, who first reported the news. These bankers figure there's little chance Zuckerberg will agree to sell to anyone but the public in the next few years, but that "putting out subtle signals," as Swisher reports the bankers call them, is worth the effort if they pay off. Last fall, Microsoft purchased 1.6 percent of Facebook for $240 million. Unsolicited advice for Zuckerberg: Be careful with the high-fives.