As the other replies say, git is already decentralized. What we need is a decentralized way to recognize one of those mirrors as the main one. I think gitchain: http://gitchain.org/ was supposed to solve that.
Read two books by him, both had the same exact plot except for locations. There's a man, loses his cat, loses his wife, loses his job, and then there's something magical that is somehow related to the Manchuria war.
I always felt bitcoin was more about replacing paper money than replacing banks. Banks give you interests, Bitcoin just sits there and the amount (in bitcoins) never changes.
Transportation was a solved problem when horse carriages were invented. Every solved problem can be solved even better. Isn't that what most startups are about?