> I think one of the reasons the torrent protocol is not built-in is that it's simply more complicated and the user experience is not as good.

That's self-fulfilling - if it were built into the browser, there's no reason you'd really have to know.

(Presumably you wouldn't run into the "zero-seeders" problem if the servers acted as seeders - they're currently serving 100% of the file anyway (without torrenting), so torrenting would only reduce that.)