Ted Nelson had some great thoughts, but fell short on implementing them. Nelson's Xanadu stands for the impossibility of implementing a perfect system. One cannot implement a perfect system, b/c anyone's idea of perfection must necessarily confront reality. Nelson was never willing to compromise to reality. I get the sense that Mr. Yarvin is totally willing to compromise in the face of reality, and has already done so in many respects to get this far with urbit.
Another important lesson is not to take decades before trying out things end to end. According to second hand report, the API to connect a UI to Xanadu was very complicated, way too complicated to expect wide adaptation.
Another lesson is to avoid too long a stealth period.
I'm not sure that Xanadu's stealth period was intentional. Maybe only a few people really understood what Nelson was talking about, at least until the Web came along and it was clear that Nelson was really on the right track philosophically. He could've run a superbowl ad every year until 1990 --most people would've shrugged their shoulders and wondered why this crackpot was wasting so much money on a silly piece of performance art!
