Comment by InvisibleCities

Dropbox has the same problem a lot of the moderately successful unicorns have; it's a good product managed by smart people that would be much better off as a right-sized stable lifestyle business a la 37 Signals / Basecamp than as an attempt at a world-beating massive-growth juggernaut like Google or Facebook. Unfortunately for them (and Evernote, and a whole host of others), once you've signed that deal for the huge late-stage VC cash infusion at a fantasy-land valuation, there's no going back.