Yahoo employees say Filo is both well-liked and respected within the company. Filo acted as interim CTO last year before Aristotle Balogh was hired for the job. His value to Microsoft is his longstanding relationship with Yahoo's engineers -- which Microsoft needs. "I think Filo is really not given enough credit for how much the engineers love him," says Eric Jackson, a Yahoo activist shareholder. That said, keeping a billionaire founder around won't be easy for Microsoft.