I would agree that the weak support for social software in MOSS 2007 will not have a significant impact on its adoption - people are buying into a stack (or platform) and not feature/function capabilities. But, what I do fear is that IT organizations will decide to sit back and wait for Microsoft to deliver these capabilities and that likely will not happen until the next release (2-3 years perhaps). What I also fear is that IT strategists will not be open to examining solutions from best-of-breed vendors in this space that specialize in certain aspects of social software. For those business requirements that cannot wait 2-3 years, decision-makers need to consider alternatives that may be tactical or in some cases, strategic if one believes that Microsoft will not deliver something within a reasonable planning horizon.
I think this also illustrates that it takes Microsoft quite a long cycle-time to deliver software that is cutting-edge at the point where capabilities are locked-down in the development cycle but can sometimes end up being behind the curve (e.g., blogs, wikis), when the product is actually released. Finally, we will see how good a technology steward Microsoft is as it builds out an ecosystem of partners around SharePoint Products & Technologies. If vendors cannot integrate well to construct social software solutions on top of MOSS 2007, then one begins to wonder about the modularity, extensibility and interoperability of the platform itself.
Some how I doubt that this will have a major impact on the adoption of Microsoft Sharepoint - afterall, organisations aren't choosing Sharepoint primarily it for its social software capabilities. But not only, as Gotta suggests, will there be "numerous smaller vendors that have the opportunity to gain some market attention", but for those shops who are tied to an Microsoft-based intranet play they will continue to experience tension between their technology strategy and their user community's wants while this vacuum continues.