This is certainly useful, but better would be something that saves entire web pages into a searchable archive, like the Evernote web clipper. The reason is that I sometimes find that my highlights and notes were missing something, and to get that something, I have to go back and reread the original. This can be hard to do if you rely upon that interesting page or tweet to still exist on the ephemeral web.

Also, when I write notes, I almost never copy in chunks of literal article text. Instead, I highlight while reading, and then go back through the highlights and write down points in my own words. But maybe I'd like to somehow link to those highlights...