Sonic.net, in the ISP market. They spend quite a bit on customer support, and use it, where they can (locally, mostly) as a feature.

Back in the day when they were reselling AT&T DSL (which they are doing again, I hear), it was a big bonus to get AT&T DSL at the same price, but not have to deal with AT&T almost ever. Let a third party deal with that and provide better service for the same cost. Win.

Full Disclosure: I've worked at Sonic.net multiple times in the past, ranging from customer support when in college, to their operations and system administration department more recently. I have fond memories of it, and count it as one of the best places I've worked, but I'm not employed by them currently.