I downloaded the latest version of facebook app for my blackberry curve. For some reason, I now see a little icon with "1" next to it (up next to the time)
At first, I thought it was a new feature - where someone had sent me a message, or written on my wall - but neither of those were true.
Alternatively, the first message that you receive when you download Facebook for the first time, or upgrade your existing version, is an automated message from Facebook itself. Make sure that you have opened the message, that way it show as read, and disappears from your notifications.