Utilizing p2p tech is not illegal. It is illegal to redistribute copyrighted content without authorization- and we are working to build this into the protocol so that peers will respect copyright by default. People can redistribute at their own risk. I'll be the first to admit that this is complicated, and we have a long way to go in this regard.

Plus, the vast majority of people will just use the web frontend, with a peer on the server. Most peers can be hosted by content creators and tech-savvy friends+family.

Almost every machine in the world participates in at least one peer-to-peer network: Windows Update. There was a time when the Steam client also used bittorrent technology, not sure if they still do.