I've been after Tantek to explain Whistle (his url shortener) to me for a while now, and I was glad that it fit in with this series of questions. I particularly liked his point about the url being expandable by any third-party because the algorithm is published.
Obviously this prevents some "monetization" of the shortener, but that's the whole point - to prevent your links from being beholden to a single provider.
I'll be continuing the series of interviews as we work through the 10 basic components of Tantek's personal DiSo 2.0 vision.