I don't really think the torrent sites are the main problem anyway (though some of them can generate traffic in megabytes per second, for a single torrent) - botnet that send spam and do DDoS are worse; even if their total traffic is smaller (which I doubt), the amount of and nature of the connections they make put more load on servers, and perhaps some of the smaller routers as well.
Another big factor, that have nothing to do with the darker business on the web, are those sites on shared hosts where capacity is oversold. Considering how slow the aforementioned flatassembler.net site is, and asmcommunity.net as well, I would think POWWEB (where both are hosted) has started overselling.
