"what would lead a person of reasonable caution to believe that something...."

And a reasonable person would say that it MAY have come from somewhere else because everyone has this feature built into their client.

Now, if you want to sue EVERYONE who uses Gnutella, and call it a conspiracy, that might work but it's a long shot.

By the way, probable cause is used for search warrants, do you really think the police are going to issue a warrant when the RIAA simply asks? This is a civil issue (as in $$$, fines etc...)

In this situation there is more probable cause to believe that the file is NOT on this guy's computer. And the more common knowledge about this feature is given out by everyone, the more likely a warrant wouldn't be issued!

Now, are there substantial legal uses for this?
Are there any legal uses for Gnutella in general?
Are there any legal uses for the web?
Are there any legal uses for anon remailers or anon surfing?
Do people use these anon systems? Could it be millions every day?
How about proxies? How about anon proxies? How about public proxies?
So why not anon Gnutella?

The guy who programmed those anon features for the web should go to jail and be sued by RIAA/MPAA or the like ! How dare he!