A month or so on and the decison to do so is now looking less and less valid. There are growing examples of very good sites set up that just haven't attracted users to build up the required critical mass.
E.g. Conde Nast's flip.com project:
However, all is not lost... potentially due to Open Social...
This common way of interfacing with multiple websites now makes it possible to have all your Social Media data separate from the site you are using. In effect this could make the barriers of site sign-up and subsequent usage a thing of the past.
It may therefore mean that having some form of Social Media on every company website is soon so easy to implement and manage that it will become the next 'must have' bit of functionality.