TorrentPeek – Query inside torrents without downloading them entirely
github.com
github.com
I see potential for this specifically if combined with BEP46 (http://www.bittorrent.org/beps/bep_0046.html).
Essentially, if we can update torrents via DHT mutable items, we can have distributed sites - similar to ZeroNet.
However this brings something new to the table, sites that can be queried without having to fully download them.
Since SQLite also supports FTS (full text search), you could literally also have a search engine -- imagine Wikipedia releasing their dumps in this fashion. Users could not only help host it, but also query for info in a timely manner - even full text search queries.