The web is already decentralized, but lack the convenience of Facebook et al. where you have a virtual identity, a friend list and can choose who get access to

The web is already decentralized, but lack the convenience of Facebook et al. where you have a virtual identity, a friend list and can choose who get access to your images etc. This can however be accomplished with something like SSH keys, where your "friend" list is basically a list of public keys. And a small daemon that will let "friends" make queries like "is this a friend or a friend", etc. With a identity system in place, other things get more easy to solve, like spam, and micro-payments based on chain-of trust and reputation. I also think it would be fairly easy to implement in current web tech like browsers and http servers, e-mail servers, and chat services. Note that your id will only be a hash (public key), and you will thus be anonymous until you tell others that this is you, and the client software could also ask the user before giving it away to a server. It would also work with something like TOR, where your IP is hidden, and the hash is your fingerprint, witch you can change whenever you want.