How Do You Scale Great Customer Service?

As online technologies continue to explode, the question of how to provide great customer service becomes more and more relevant. Facebook has 300,000,000 users and about 1,000 employees. Even putting users aside, (I know readers won't like this, but it's a business reality) Facebook has hundeds of thousands of advertisers for that small number of employees, a pretty huge ratio in a service-orieneted business (which advertising and marketing is).  So does Google, and Yahoo. So will Twitter, when they finally turn on their revenue-stream. So how do you provide great customer service at scale? Google has a world-renowned easy-to-use self-serve platform for purchasing its Adwords product - Facebook's self-serve Ad platform isn't there quite yet but it's on its way. Clearly, the easier an interface in the first place, the better an FAQ, the more helpful videos, etc, the less of a need for great customer service.

But what about when there are problems, or questions, or concerns? At what point is it important to provide a human being at the other end of a phone (or live chat)? Better yet, at what point is it profitable to provide a human being at the other end of a phone (or live chat)?

Great technology can clearly be automated - and sold and provided - to huge numbers of customers. But can great customer service be delivered to huge masses of customers? Can a search company or social network provide Zappos-like customer service to advertisers? What do you think?