www.joomlapolis.com/component/option,com_joomlaboard/Itemid,38/func,view/id,7645/catid,13/limit,6/limitstart,0/
This plugin shows a rss feed in a tab. Since both twitter and face book export rss feeds, the plugin could be modified to work for this.
However, after trying a few times to get it to install it looks like it is no longer compatible with the latest versions of joomla and/or CB.
I'll try taking a look to see what's wrong, but, well, I'm not exactly a developer so I doubt I'll get far.