Eric, ideas are cheap and execution is hard. I happen to believe that you're completely out to lunch if you think you could build this in a practical, scalable way that is useful in the ways I describe above.
However, I'm open minded and you seem confident — so if you believe that you're sitting on something, please feel free to share how you'd structure such a service. If you get it right, I'd pay you a lot more than $5, as long as it had the blessing of Dropbox (ie. doesn't get API throttled and isn't going to get cut after I integrate with your tool).
I was being facetious -- I do think a service like this could be built, but I am working on something else. Sorry if it came off offensive (I'm not out to lunch).
Really I meant to point out how the pattern of web apps connected via REST API to desktop folders/files is interesting and will enable a lot of data management schemes that were previously much harder or obscure.
However, I'm open minded and you seem confident — so if you believe that you're sitting on something, please feel free to share how you'd structure such a service. If you get it right, I'd pay you a lot more than $5, as long as it had the blessing of Dropbox (ie. doesn't get API throttled and isn't going to get cut after I integrate with your tool).