There are currently 456 million active users globally. Facebook has managed to connect with people and influence culture, creating a social phenomenon. Your Facebook identity is the true you - what you say and share reflects how you want to be seen and this will effect your real life.
The move from "Become a fan" to the "Like Button" is representing the "Like is an extension of me and my interest" which represents our core values. In fact, people click "Like" almost twice more than they click "Become a fan" everyday. This change makes it much faster for brands to build a wealth of new followers.
Facebook fans are self-segmented group of highly valuable customers. We need to understand the value of fan as well as their behaviour to develop a long term strategy. Facebook is a great marketing environment, people enjoy interacting with brands that enjoy interacting with them. The race is on to build a fan base and websites that are integrating Facebook Connect and Facebook Like Button.
Source: Uniqlo and Naked - Facebook Marketing Workshop