If LinkedIn is the new Rolodex, what is Facebook?

But the giant of social media, the reigning champion is Facebook. Major marketers are putting big bucks and mega resources behind it as the powerhouse for reaching target audiences with meaningful, referrable and potentially viral content that drives sales. While it began life as a Yearbook, I no longer feel comfortable using that as the analogy. What is Facebook in terms of the New Rules of Marketing? As I ponder this question and view my Facebook friends and businesses and their status updates, I'm thinking perhaps it has morphed into more of a magazine. People magazine? What old medium do think Facebook most resembles?