Why hasn't Dropbox extended its main service with something like this yet?
Incredibly simple apps like puu.sh and Skitch have taken off as separate apps and there has been a scattering of Dropbox-integrated third party tools, which I typically have to give away my Dropbox key to use. There's so much data on the web that is difficult to pull out of the cloud, and Dropbox is in the unique position of bridging these two realms.
Dropbox has a lock on the position of market leader in file storage, but they haven't built a platform. There was an article a few days ago which described how Dropbox is a feature, not a product, and the whole company would be put out of business if Apple/Microsoft/Google just rebuilt the functionality (a bit hyperbolic, but worth a thought). But I don't think there have been more than a few features since I started using Dropbox a few years ago, and it's not for a shortage of engineers.