(NOTE: This isn't meant to only cover file sharing, it's meant to establish a network, which is a VPN which allows you to do anything you could do over a normal network)
Alliance P2P is a file sharing network (Program) which is decentralized. Meaning, there is no central server anywhere. It connects to the IP address of another computer, which has it installed and then gets the IP addresses of other computers on the network. As long as every computer on the network has not been shut down, it can rejoin the network at any time by knowing those IPs. After it connects to the network, (Every Ubuntu computer in our case) it gets a fresh list of IPs It establishes connections with them and then networks the computers which share the same encryption. (Basically using the same technology a normal network uses, except adding an encryption allows it to only be used by computers which know that particular encryption (basically an advanced netmask) on any network Internet/LAN) I believe Ubuntu should adopt this technology to allow it's users to establish virtual private networks between each other, This would allow networks which have a high immunity to government censorship, as well as allow a network to be permanently established, no matter what IP address each user was on, without having to go through a third party to set it up. As stated above this VPN would work both on the Internet, and on a LAN.
Examples: Bob is on computer A and Jane computer B which are both connected by this idea
Computer A is at the library and needs a file from computer B. It get's it. That's good. So now computer A visits their work place and computer B visits the gym. As soon as they are both powered on, the IPs on both have been changed! Without having to use a DDNS address or a central server which may become overloaded, they simply search the internet, until they find each other. Network re-established.
Computer A and computer B need to work on a presentation together for a company they haven't ever been to. The company has a LAN, but doesn't have the Internet. The computers still search out and find each other, because they are programed to look for each other and not what medium is used to get to each other.
Lastly, A and B share a cab. They want to share the presentation. They establish an adhoc between each other, which instantly gives them access to the folders which they had access to in the first and second example.