Lots & lots!!! lol
I've forgotten how to count them all. After all, I only have 4 fingers.
But there's lots of p2p networks out there, not only Gnutella. Gnutella is only one p2p network.
BTW for LW users, see the top right corner here
http://www.limewire.com/english/content/uastats.shtml
But also keep in mind, a search using LW does not locate "all" LW users on the Gnutella network. That would require too much traffic & your search would be so incredibly slow to return results. How do I know, because I used a different p2p program that offered you that option. I could be waiting 30 mins or over an hour for a single search to return all the results. LW gives back faster results compared to no. of users despite a search might only actually find a % of them (but a considerable %.) That's why searching techniques is important to reach the others that might have the file you're after. There's links on the forum about how best to do this. Varying one's search, browsing, etc. all play a part.