SharePoint is a huge factor in the enterprise social networking environment, even though analysts agree it falls far short of the other products in this category, at least as an out-of-the-box experience. SharePoint 2010 holds more promise as a platform for building social applications, adding basic building blocks like profiles and activity feeds.
With some customization, or the addition of third-party social software products, SharePoint can deliver a social experience that takes advantage of an enterprise's existing investments in the portal and dovetails with other Microsoft collaboration technologies, such as Lync unified communications.
Even when SharePoint is not at the center of a social collaboration strategy, it is almost always in the picture somewhere, just because SharePoint has been so broadly adopted as a portal, content management, and collaboration platform. Other enterprise social networking products are judged, in part, by how well they integrate with SharePoint.