Microsoft will begin its third 2009 layoff round as soon as this morning, TechFlash reports, because the software giant's growth has slowed. Conference rooms are already reserved. If you learn anything about the reboot, email us. (UPDATE: Social networking hit.)

Microsoft has said it will lay off 800 in this round. A tipster tells us it shed at least eight 11 people from the Cambridge, Massachusetts office of its "FUSE" social networking research initiative, announced just last month by Microsoft chief software architect Ray Ozzie. Our tipster said the Cambridge operation has been going for a year and a half, though, so it seems likely this is part of the restructuring that created FUSE from three existing Microsoft groups. This is the group, by the way, that brought Twitter search to Bing.