Sure, this is internet and everyone can sniff an unencrypted data stream (like gnutella is), everyone who is between you and your opponent peer (your ISP and many routers are).

a) Gnutella P2P filetransfar should be encrypted (Queries/Hits not), https over http would be possible with gnutella protocoll.
b) Swarming files should be implemented to spread content, random 500 KB partials of most requested files would be fine even for modem users.

Right?