"you can already build such a system yourself quite trivially by getting an FTP account, mounting it locally with curlftpfs, and then using SVN or CVS on the mounted filesystem"
Oh, thanks bro.
It is probably the most cited HN comment of all time (https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...). Entire rants have been written about it, and not nice ones. Fortunately the commenter has been a good sport about this over the years, given that it's hindsight fallacy.
People don't remember this now, but before Dropbox succeeded it was widely taken for granted that file synchronization was pointless to work on because no one would ever make a business of it. Joel Spolsky wrote a famous post mocking the idea: https://www.joelonsoftware.com/2008/05/01/architecture-astro... ("Nobody cared then and nobody cares now, because synchronizing files is just not a killer application. I’m sorry. It seems like it should be. But it’s not.") In 2007, it was common 'knowledge' that most consumers wouldn't want such a thing and technical people would just roll their own, so a viable business couldn't be created out of it. In BrandonM's comment (https://news.ycombinator.com/item?id=9224), the word "app" referred to YC application, not software apps, and you can see in his point #3 the widespread assumption that no one would ever pay money for this.
The surprise was that Dropbox proved the common knowledge wrong, but that didn't happen till later. When YC funded Dropbox, it was because they believed in Drew, not file synchronization, which is also information that wasn't available till later. So if we are to look at that thread fairly, in context, we should see it as a successful conversation with a graceful ending, rather than mocking someone for not knowing the future.