Casey Newton has written another great piece about Dropbox.
His first was an article about how other companies such as Google, Microsoft, and Apple have begun to bake Dropbox's core file-syncing & sharing functionality into their own services.
This piece covers Dropbox's recent announcement that they would be cutting off the Mailbox and Carousel apps in order to focus on their main product.
I remember when Mailbox came out. I signed up for the beta. It really was innovative, and its influence is seen all across mobile email clients today. Just like file-syncing and sharing, Mailbox's features were cannibalized by Dropbox's competitors.