It's good and all, but you're telling me that no significant innovation has occurred over the last 5 years (since Dropbox was just a Show HN) in start-up land‽
Even Dropbox has stagnated, IMO. Still no granular access control. I still can't share a document as read-only. I know they claim it's because each OS handles access controls differently, but it seems nuts to me that I can host the same file on S3 as download-only with an expiring link.
Dropbox is great for personal sync across devices, but it still isn't a group file sharing solution. Again, my opinion, but I think it ought to be both.
Wuala has many, perhaps all of your desired properties.
The two killer features for me are client side encryption and selective
syncing, you can separate define for each client which folders are synced.
Wuala even supports streaming of files. With their virtual file system you
can start reading not completly downloaded files.
The disadvantage of all of this is the increased complexity in the user
interface. That's the beauty of Dropbox, the simplicity. But now,
after getting used to Wuala, I wouldn't want to miss it.
Right click on the files/folders you want to share read-only, go to the Dropbox sub-menu, and click "get shareable link". I use it all the time. I think it's exactly what you're describing?
I only see "Browse on Dropbox website..." and "Share this folder..." in the contextual menu.
I don't doubt you at all – I can see in their documentation that the feature exists. I just can't seem to make it happen.
Update: Looks like this only works for files that are already public, as far as I can tell. I managed to find "Copy public link..." if I right click in the Public folder.
Update 2: What a mess! Here's the doc that explains this buried feature: https://www.dropbox.com/help/167 I was able to switch to the "new sharing model", whatever that means. I still can't generate the link, though.