While this is true, browsers could benefit from a "bittorrent-lite" implementation. You get the files from a server, but they come with metadata like a .torrent file, which includes hashes for small chunks of the file. Downloads are automatically checked and can resume anywhere. It could all be transparent to the user. Really, it's amazing this isn't the default way to download yet.
Resuming fetching multiple unfetched fragments of a resource is already possible with HTTP range requests. Checking the entire file can be done if the server provides a Content-MD5 header (though I'm not sure actual client use of this is widespread), and checking parts of it is infrequently useful by itself to the processing application and would be highly application-dependent even if so. The big win of BitTorrent is the distribution of available channel capacity over the swarm of downloaders; if you're not going to use that part, HTTP does quite well by itself.
