Did you see that ThePirateBay switched from central trackers to DHT with
peer exchange?

http://thepiratebay.org/blog/175

We all just took one more step toward the darknet. The even more
interesting of the two is actually the peer-exchange (PEX) component:
DHT is just a distributed version of a central tracker; it tells you the
same thing as the tracker, just in a way that can't be stopped. But PEX
actually allows you to participate in a swarm without "announcing"
yourself: so the number of people actually downloading/uploading a given
file becomes even harder to measure. The combination makes torrents not
only unstoppable, but moves us closer to them being untraceable.

Next up: default-on encryption in all the major torrent clients (putting
a nail in the coffin for ISP sampling), and then some form of
digitally-signed DHT-based indexing/browsing (such that centralized
tracker sites become unnecessary). At that point it'll become
essentially impossible to figure out what's being shared and to what degree.

The only chink in that armor is you could still target individuals by
just starting to download something and see who you connect to.
Granted, the RIAA has already given up on this approach, but there's
nothing to say they (or someone else) couldn't start again. If they do,
then it's just one more upgrade cycle away from onionskin routing and
voila: the darknet is born.

-david