Every time someone on HN says "you don't need x, just do a, then b, then c and you'll get something similar" I'm reminded of this comment: https://news.ycombinator.com/item?id=9224
Dropbox is just a hosted rsync server really [0]. The service has value, the technology didn't really require a new protocol except for lock in purposes.
I'm not saying that a service that takes existing ideas and makes them easier for people to use is bad, I'm saying that the open protocol people are calling for already exists, but because they have tech-brain they'd rather build a completely new protocol because it's more fun.
I dug around many years ago into dropbox. I actually found rsync was being used in at least some of its functionality. I doubt that remains the case, but it made me smile when I found it as it made a lot of sense at the time.
