Former Microsoft exec Paul Maritz has replaced company co-founder Diane Greene as CEO of VMWare in a move which coincides with a warning of lower expected revenue forecasts for 2008.

While VMWare has been handily cleaning up in the virtualization sector, renewed competition from Microsoft and growing acceptance of outsourced cloud-based services may both have a hand in the lowered forecasts and Greene's ouster. In Maritz, the VMWare board may be attempting to gird itself for the coming battle Royale with Microsoft's newly released Windows Server 2008 Hypervisor virtualization platform... the first Microsoft virtualization offering which offers any significant competitive advantages over Vmware's platform.

Some analysts are suggesting that this is a more or less inevitable stage in the company's growth, and that while Greene provided good direction and management for a startup focused on technology, it may naturally have been time to switch to a more marketing and relationship focused CEO. That may be the case but the timing is unfortunate, lowering confidence in the company just as Microsoft is making its most significant move into the sector in years.