I've actually heard that it's also used by smaller businesses as a way to communicate with their target audience. So, for example, if you are a chain of cinemas, you can let everyone keep up with when/where you are going to release the next films. If you are a retailer, you can advertise when the new products are in.
A bit like they did in the past with email newsletters. (Though a lot better: for a start, it doesn't spam your inbox, which can remain for more important matters).
Absolutely! Fan pages are a good way to stay in touch with existing customers/fans. Often, companies also provide special offers, early bird previews & discount coupons to facebook fans. And yes, it is replacing newsletters in some ways. However, I think most firms 'play safe' and send their 'news' through everything - twitter, facebook & email. So, if you're following a brand on multiple channels, the clutter is only compounded!
A bit like they did in the past with email newsletters. (Though a lot better: for a start, it doesn't spam your inbox, which can remain for more important matters).