This is a great idea, but in keeping with the open source and open data pieces, the model that
quotebacks.net is using has some advantages. In their case, they're providing full HTML markup with classes for styling (or markdown as an alternative) along with a small javascript tag which points to one of their servers and handles the look and feel of the "embed". The benefit of this is that if
quotebacks.net ever goes away, you'll still be able to see a reasonable fallback of the content on the embedded website, otherwise on a server-only based model, you'll potentially have millions of embeds that break or disappear if the third party server disappears. This is also an embed model used by Twitter and several other social media services.