It turns out that _Mad Men_ has a huge Twitter presence. Many of the characters are on Twitter: Don Draper, Betty Draper, Bertram Cooper, Roger Sterling, Peggy Olson, Joan Holloway, Pete Campbell, Trudy Campbell, Sal Romano, Harry Crane, Paul Kinsey, Freddy Rumsen. That's too many people to add to my Twitter feed (they'd take it over!). I'm debating making a separate account (perhaps as a minor "Mad Men" character) to watch the exchanges.
There is also a website, We Are Sterling Cooper, that links to many interesting articles about using social network tools in advertising including the "Mad Men" Twitter accounts (which weren't all by the network).
One fun article there that wasn't directly related to this was The Eight Most Entertaining Fake Twitter Users. All Hollywood folks (characters, actors, etc), but a heck of a lot of fun.