Many have reported that Dropbox bought Mailbox. Mailbox is a new iOS email app that has gotten a lot of press. Plans are to move Mailbox to other operating systems. Question one should ask is: why did Dropbox need to buy Mailbox?
On the surface Dropbox appears to be one of the most successful apps in recent years, right behind FB and Twitter. However, a great app does not make a successful company that can sustain double digit growth for several years after an IPO. Dropbox has added new features recently but those features look to me to be more related to competition and less related to growing revenue.
My view is that Dropbox needed an additional product to maintain attractive revenue growth rates. Adding another product is one way to move toward being a company and not just an app.