The fact is most videos are unpopular, so they don't have a very high bandwidth requirement. Those that do have a high bandwidth requirement are the popular vid

The fact is most videos are unpopular, so they don't have a very high bandwidth requirement. Those that do have a high bandwidth requirement are the popular videos that will be seeded by more nodes in the network. Typically this popularity is brief, so as the popularity fades, nodes can switch to hosting other content without a dramatic uptick in bandwidth usage for other nodes. The system works as long as users typically seed approximately the same amount as they leech.