BitTorrent is a protocol for distributing files. It identifies content by url and is designed to integrate seamlessly with the web.
It is advantage over plain HTTP is that when multiple downloads of the same file happen concurrently, the downloaders upload to each other, making it possible for the file source to support very large numbers of downloaders with only a modest increase in its load.
BitTorrent is a free and simple to use software product which addresses all of these problems.
The key to scaleable and robust distribution is to tap the unutilized upstream broadband capacity of your customers. Their contribution grows at the same rate as their demand, creating limitless scalability for a fixed cost.
BitTorrent is not just a concept, but has a functioning implementation, already capable of swarming downloads across unreliable networks. It has been embraced by numerous publishers to cost-effectively distribute to millions of users.