gnutella is a protocol. See http://www.limewire.com/english/content/uastats.shtml for the list of programs (vendors) that currently use it.

http is also a protocol. So Firefox, Safari, Internet Explorer and other browsers are programs written to use the http protocol. Protocols are just the rules needed to make connections . . . (wish it were as simple as that sounds)

Re the "safety" question--I'm on a Mac so really have no problems with "safety." Once the writers of malware focus on OS X, there will be problems, but nothing like the problems the poor Windows users have to put up with.

I've used p2p for a while:a couple of gnutella clients (mostly LimeWire), bitorrent, Azureus, and a few years back some others that I forget. I've never had a virus, a dialler, a trojan, or whatever else you'd call malware.

Others can tell you more, but p2p nets are just one of the many ways nasty people can use to make your computer do what "THEY" want.

Practise "safe surfing" and email, web browsing, and p2p apps work just fine.