I really don't understand Dropbox. For the average user that wants to store, say, a few tens of GBs Dropbox costs $9.99 a month. Nevermind it gives 1TB total, most people don't need that much. iCloud, for example, costs $0.99/month. That's an _order of magnitude_ more expensive. Whichever way you slice it, it seems like Dropbox's core user base, that pays but doesn't take full advantage of the 1TB is bank-rolling the…
As soon as you try their competitors (Drive, Box, iCloud) you find out just how utterly crappy they are as soon as you need to share files with other people. Dropbox does it seamlessly. Bankrolling free accounts so students can have their thesis backed up is a small price to pay for that.