Couldn't have said it better.
I think this was pretty shallow analysis by the author, but to his very first point - I do think it's the elephant in the room for a lot of startups. One of the most consistent pieces of advice/feedback I've heard from serial entrepreneurs and VCs is to stay razor focus.
Multi-platform is key. Shared folders can be used to collaborate not just with people, but with Linux servers too. I let users send files to my site by sharing a folder with it. I predict a lot of services will do that in the future. It's an easy way to give people offline functionality.
It might work "awesomely" one some platforms, but the Nautilus integration is pretty buggy - it was a nightmare to try to get it working on my Ubunutu 09.04. I ended up having to just use the command line utility a user wrote.
It's simple (automatic) to use but not simplistic. Its power ramps up when you need it (file recovery) and fades away when you don't.
It doesn't get in the way (with advertising, installing crapware, charging micropayments, proprietary restrictions/formats, etc.)