I find it funny that Dropbox is used as the example of HN nerds saying how they couldn't understand how something was a business because there are so many easy ways to implement it. If it never made money, it wasn't a business.
Regarding USBs, Dropbox's messaging at the time was "throw out your USB drives", and this was before smartphones or ubiquitous dependable network connections. At the time, if I had to give a presentation in a university classroom, Dropbox wasn't moving the bar much on that particular problem.
Is your ego really that fragile that you can't admit you made a mistake judging a business?