Currently, all sites have a official Twitter account run by a SE bot. I suggest that, to best harness social media for the benefit of the SE Network, each site should have official Facebook and Google+ pages as well. As both these sites now support hashtags, the same posts that go on Twitter can be posted on FB and G+ pages. This way, no extra work will be needed to run either of these associated pages.
As is well known, social media can create a buzz around new things and popularize them much faster. The bump in views and userbase that will be gained from these pages will have a major impact on beta sites, especially newly launched ones.
It will also help in spreading awareness about the SE Network as there are a huge number of people who are interested in specific subject areas and have questions to ask, but dont know of the existence of SE sites.