But the danger is that we will wake up one morning and find that the general public have given up searching on Google (and Bing for that matter) and decided that Facebook (or whatever is the flavour of the month) gives them better results. Impossibele? I think not.
Why not spread the zone of influence of your websites to help insure that whatever the public does, you already have some presence in their chosen source of information?
Even if the likes of Google and Bing do remain all important over the next ten years or so, although unlikely, does anyone outside of those two organisations really know how they view the importance of social sites and the effect on their SERPS?
We have no idea at all.
My guess is that social sites like Facebook will become increasingly important to how Google rank entries in the SERPS.