The NZ Herald tech columnist Peter Griffin writes the following:
I’ve been back and forth on email over the last few weeks with a Herald reader who believes his internet connection is being throttled back extensively because he is a big user of peer-to-peer file sharing systems. I should point out that he’s a legitimate user of such services – he’s a sound engineer and needs to send and receive big files. P2P is an efficient way of doing this.
“P2P” usually refers to a decentralised non-server based network, and these days usually also means a swarmed network like bittorrent. So, unless the sound engineer in question needs to send and recieve files to and from THE ENTIRE INTERNET, using a P2P network to move them around is the exact opposite of efficient.
If you want to send your mum an avi of you beatboxing the theme song to Super Mario Brothers, you open your IM client and send it directly, you don’t create a tracker for it, post a torrent link to the Pirate Bay and them IM your mum with the torrent URL. I am aware that strictly speaking, IMing your mum is a peer to peer transaction, as there’s no server involved, but that’s not what people mean these days when they talk about P2P.
 “You know Stewie, this reminds me of the time I described a tedious pop culture based non sequitur.” .. okay, he’s not THAT Peter Griffin. I bet he gets that a lot, though.