SharePoint 2010 continues Microsoft's strides toward its Software Plus Services (S+S) strategy. Microsoft has three flavors of hosted SharePoint, the most common of which is multi-tenant, or co-hosted, offered through Microsoft Business Productivity Online Standard Suite (BPOS). In its current iteration, this service offers functionality basically equivalent to Windows SharePoint Services (WSS) 3.0 plus publishing. SharePoint 2010 has been designed to support richer multi-tenant functionality, including service applications such as Search, Managed Metadata, and My Sites. It's safe to expect that multi-tenant hosted SharePoint Online will extend such capabilities to its subscribers after the service is updated to SharePoint 2010. I expect that SharePoint Online will come admirably close to feature parity with internally hosted SharePoint farms.
The second of the three hosted flavors of SharePoint is SharePoint for Internet sites. Microsoft has revealed new multi-tenant options for hosted SharePoint 2010–based Internet sites. It’s currently not possible to host public-facing, anonymous-access websites on the multi-tenant version of SharePoint Online. These new Internet offerings will let businesses publish their public-facing websites on SharePoint in a robust and secure infrastructure hosted and managed by Microsoft.
The third flavor of hosted SharePoint that Microsoft offers is dedicated SharePoint hosting for large enterprises. Through this offering, the level of functionality isn't limited by the fact that your SharePoint applications are multi-tenant. Instead, you can do anything and everything SharePoint can do because it’s your server. Microsoft simply hosts and manages it.
Finally, there are aspects of SharePoint and its Office Web Applications integrated into Microsoft Office Live Workspace and Windows Live, which expose SharePoint functionality to small-to-midsized businesses (SMBs) and consumers with a free-to-the-user, advertisement-driven model. The experience with Office Live is already so rich that I can only blame poor marketing by Microsoft for any inroads made by Google in the SMB collaboration market. SharePoint 2010 ups the ante, and I expect Office Live will provide Office Web Applications (Word, PowerPoint, and Excel), for free to the same markets.
The takeaway for your enterprise is that hosted SharePoint has come of age and, unlike other companies' web-only offerings, Microsoft gives you the flexibility to mix and match internally hosted and externally hosted SharePoint versions. Be sure to give careful thought as to how you can leverage both to meet your strategic objectives.