Dropbox is only a "failure" if you require continuous growth. Let's pause for a moment and think: why do we require that? I know, markets, etc, but Dropbox could be a pretty good medium-sized business and be just fine.

Well, another way to look at it is that Dropbox is a failure because instead of doing one thing right and optimizing the heck out of it, it tries to do many things, most of them badly, in the name of growth.

I hope somebody will start a Dropbox competitor as a bootstrapper, with a long-term outlook, no VC funding, and no crazy growth targets. Just do file sync right without eating so much CPU and battery, and without pestering me with useless add-ons, and you'll have my money.