Interesting. That was a real question, btw. I've never used BitTorrent. I understand the concept, but got bored with it all right about the time Limewire was ready to bite the dust. In that setup, you did upload what you had already downloaded - but not immediately. IIRC, it waited until you had the entire file stored.
But, they had a kind of odd way of users protecting themselves concerning original uploads. Files would be named incorrectly, almost universally. Sometimes, it was near genius - you had to stick the genre, and sometimes get the name...not correct, certainly. But you would use a file name that was a real name, and also suggestive of the actual file you were uploading. Like, if you wanted Frank Sinatra, doing Witchcraft, you'd get a file that said it was Dean Martin singing something with Magic in the title. That sort of thing.