Why BitTorrent causes so much latency and how to fix it

Anyone VoIP or online gamer who has a roommate or a family member who uses BitTorrent (or any P2P application) knows what a nightmare it is when BitTorrent is in use. I decided to do some research on this and ran a series of tests which resulted in some very interesting data.
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very very useful article

Definitely something people with cheap routers should go check out. Amount of connections they handle are very different from large scale ones.

Theory is one thing, but you can really only apply QoS (Quality of Service) rules to the outbound traffic that you are originating. Your inbound traffic, originated by others, you have little control over.

True, but inexperienced users tend to overstep their connection limits, upload limits etc so their overall speeds suffer.