Do you mean to say have HubPages as just a simple sub-section of Facebook or Google+ ?
On the one hand there'll undoubtedly be more writers and hubs that way, since Facebook for instance has 800 million active writers who will be encouraged to write. Plus article circulation would be easier and more present.
But the reason it won't happen is because the whole idea of HubPages is that you can sign up immediately to a respected writing community and make hubs that are placed independently on the internet.
If it was so that every one of my articles suddenly were in the format of: www.facebook.com/philanthropy/hubname then I would quit HP because it's no longer even resembling professional writing.
Plus, who can take an article seriously when it's from a social networking site? Even the news articles they have on there are regarded as poor quality and a waste of time.
Hope I understood this right?