Lets just say that I don't believe that decentralized dependencies scales well. Imagine a popular big application with hundreds of dependencies (think a mature Rails application) - that would either mean hundreds of simultaneous connections to github or an extremely slow serial dependency resolution. It would reach a state where github would tell us to go fuck ourself pretty fast.
Github has had this type of problem before, and it seems that they handle it pretty well. I think as long as a single repository doesn't become a massive hotspot, Github don't really mind. I'm pretty sure that go checks out dependencies direct from github for every application, so the precedent is there. Shards also caches the repositories globally, which is nice.
