I produce customer service videos, and whenever I do research, the one thing I always hear is that the basics of good customer service are timeless.
That said, what I think makes customer service different in the 21st Century is the internet, and social networking. I think the quote below sums this up well."If you make customers unhappy in the physical world, they might each tell 6 friends. If you make customers unhappy on the Internet, they can each tell 6,000 friends."
-Jeff Bezos, Founder Amazon.com
At this link you'll find other customer service inspirations