Connie Bensen sitting in Victoria BC airport alerted me to Jeremiah Owyang's recent post on his http://www.web-strategist.com/blog titled "Castles, Towns, and Missionaries". His post outlines 3 styles that companies are adopting for Social Media Engagement ( Jeremiah used the term Marketing).
Locked in the Castle
Keeping the good stuff close to your domain.
Building roads to Towns
Reach adjacent towns by enticing them with content, and provide them with links (roads) back to your land
Missionaries spread to new communities.
Read Jeremiah's post for the details which I assure are thought provoking and you will be sending his posts link around the office like I am going to do.
I am not sure if "Castles in the Air" is a common idiom here in the US. But when I was growing up if I said something that was a dream and probably not achievable then I would be told that I was building "castles in the air" . I am using the term in my title because if this is not done right SOcial media strategies will remain "Castles in the air"