Unified Communications (UC) includes new modalities such as social networking, though most UC solutions today don't deliver social networking solutions, beyond simple linkages such as blog or wiki click-to-call.
A lot has been said and written about the ROI for 'traditional' UC, but what about social networking (i.e. blogs, wikis, social bookmarks and the like)?
I think the angle that enterprises planning blog and wiki investments should consider is the value of these contextual communication tools is in making it easier to connect to co-workers that may have the skills and information needed to solve business problems. This can knockdown organizational barriers that slow down certain business processes today.
This is contrasted with unified communications that assumes you know who (by name or role) you need to reach.