Quoting Thrax

Most of them have a dozen mirrors or more. Heh.

Still... without the pages pointing out the trackers, or the sites containing the trackers, bittorrent can't work, so there is a centralised portion to it. Just in this case, the centralised part is only responsible for a much smaller list of files (I use the term 'list' pretty freely here - can't think of a more appropriate term at the minute), as opposed to open slather file sharing like Napster or eMule.

It's a much smaller target than suing all the seeders in any case.