Social & SEO: How to Handle One Company with Multiple Websites and Domains

Since social signals have become the most strongly correlating element in search rankings, at least on Google, (ref: Social Signals Again Seen Highest Correlating Factors With Google Rankings) I want to be sure that social signals are picked up properly. The complicated part is that we have one company that's publishing multiple "marketplaces". Each marketplace is unique, focusing on a different type of product and having a domain relevant to that product. So we have one company with its own corporate domain and then a bunch of marketplace-specific domains. Presumably Google is giving "social juice" to the URLs listed in the "about" of the Google+ profile or Facebook page. We can safely assume that the social SEO juice is being attributed to the main site listed in the social profile, but would it be spread across all the sites if multiple sites were listed? I would like to believe so, but that's not nearly as safe of an assumption. This would lead me to believe that each marketplace should have its own social profile, but that is a massive PITA both from the standpoint of having to customize each one and manage them all. While we could publish more relevant content to each social profile, content would be published far less frequently since we have to spread out the content among a bunch of different social profiles. Also, the likes / +1s, etc will also be spread out and fewer in number since that will also be effectively divided among a bunch of social profiles.

So if you were me, what would you do?

I know this question doesn't have a "right" answer, but I thought getting the collective opinion of Warrior Forum would be helpful, and I'm really thankful to anyone who offers an opinion.

All responders are awesome and will reborn as a dragon in their next life.