I wonder what this means for http://filepicker.io
It's validation of the market but they're not part of the deal.
To me, this is a big win for Dropbox but a big detriment to the ecosystem and other storage players. It's essentially like saying "Only works in IE6" - worked well to buy IE lock-in, but was a Bad Thing for the web. We, of course, want to help rectify this!