Also, git doesn't work p2p, it uses centralized servers. If i understand correctly, the only real difference between Twitter and this is that you have your data downloaded, so switching to a new platform is a matter of adding a new remote and pushing it there.
My understanding of this implementation is you can use arbitrary git urls to follow. That could point to any process serving data. P2P is 100% possible.
It would be smart to use a personal domain for the git url you give your followers, so you can update the hosting location without causing any disruption.