A friend of mine likes to go to LANs and like to run LANs. He has been complaining for sometime that social gaming no longer occur at LANs and in its place is leeching. Lest you think LANs have somehow turned into 19th century medical clinics, we are talking about leeching of files, which given the kind of people who go to LANs, consists of porn, porn, porn, movie, and porn.
My friend laments that he hasn't found a nice way to deal with file sharers such gamers aren't impacted, since some file sharing is required for games installers, updaters, drivers, etc. Any kind of port blocking, packet inspection, real-life-what-are-you-doing inspection are right out for the reasons of impotency, latency, and privacy.
After some discussion, we came up on the following idea to discourage, not ban, file sharers: limit upload rate of all ports. This won't affect 99.99% of gamers since games use very little bandwidth, and it still lets you download at full speed. This however impacts significantly on file sharers: the theoretical maximum downstream a file sharer can achieve is n-1 * upload_rate, which assumes everyone else is giving him their upstream bandwidth. Make this theoretical maximum low enough, and file sharers are better off using sneaker net.
There is an elegance to this that appeals to me - it exploits the fact gaming prioritise latency over bandwidth, and file sharing bandwidth over latency. It is also resistant to circumvention - because this can be implemented on the data link layer, it isn't something file sharers can get around by changing ports or using encryption.
If you know of any LANs that implement this policy, or run a LAN implementing this policy, I would love to know how well this idea performs in the real world.