Big companies NEED to use social media as a customer service tool. Social media works best for carrying on a conversation, not for sales, so this isn't surprising.
Comcast, Delta Airlines, Alaska Airlines, American Airlines, Hilton, Sheraton - all businesses I have personally had conversations with around issues in the past 6 months - all via social media. Granted, not all issues are resolved by those teams, but what agreat way to protect your brand and make me feel engaged. :)
Heck, just a few years back, xBox set a world's record for customer service using Twitter: