I like the concept of filepicker.io: a standardized widget for providing files that handles local files, remote URLs, and services people use. However, every time I read the phrase "by inserting a few lines into their source code", I think 'yeah, and one of those is a script tag pointing at a third-party server'. And sure enough, looking at the documentation, I see exactly that.
I really wish web services would start providing instructions for self-hosting all scripts.