Gnutella is ahead of any "hacking" because of the open source nature of the network and hackers are the ones programming the clients.
You can assume people have already tried to shut down the network, just as a test or just for fun, and it hasn't worked, except for that lame bogus version of bearshare vinnie put out about 8 months ago that almost shut down everything.
As soon as developers listen to requests by the users and add anon features, then the threats of lawsuits won't work.