I'm hearing an incredible rumor about David Sobeski, the former Microsoft general manager now opening a Seattle-area office for Yahoo, and I'm not sure whether to believe it. Whispers from well-placed Yahoos are that he took the job under "false pretenses." Translation: They think he's a spy for Microsoft, planted at Yahoo to learn the company's secrets. The new office is to work on something called "DataOS," the technical underpinnings for Yahoo's large-scale Web operations. Microsoft is playing catch-up with Google in Web-based software, and getting hold of Yahoo's technology would be one way to take a massive leap. There may be nothing to the allegations. But if Microsoft hasn't placed a corporate spy at Yahoo yet, I'd have to say I wonder what's taking them so long.