I'm somewhat astounded to hear they have 972 employees. I would have guesstimated somewhere below 200. Even with a huge marketing push, I'm a little at a loss for what they all do.
Edit: You were before me, so added my comment as a reply to you instead.
(Source: dropbox.com/about)
It's not just file storage for five bucks a month.
In business, usually it's possible to achieve whatever revenue you want; the hard part is getting there without a headcount/other expense basis that makes you bleed money instead of earning it.