Xeni Jardin has just written a great article for MSNBC called "Online Social Networks Go To Work" that focuses on Enterprise Social Networking. It's great to see this starting to make it out of the realm of arcana and emerge into the broader business context.
From a "how does this matter to customers?" perspective, UC Berkeley's Danah Boyd nails the crux of it:
"Salespeople know how to work their black books to make sales, and rolodexes can be a businessperson's best asset. These Web sites just take that online."
Ultimately, it's all about the relationships between customers and the people who are trying to serve them, ain't it?