For those of you who must have a technically correct example (hint hint- You know who you are), let's try this:

Consider an undividual owning a cabel subscription plan that comes with first 20 or so channels. But this guy wants all the good stuff: HBO, Cinemax, Sci-Fi, etc. Problem is, he doesn't want to pay for them. So, he buys a cable descrambler. But as most people know, these are illegal in the U.S. The primary feature of the hardware is to perform an operation that is considered illegal, and has already been established as being illegal. Most people who buy a descrambler will use it to unscramble a scrambled signal. Because of this tendancy, it has been made illegal because it does more harm that it does good. Most people will not use it for noble purposes, and most likely, there aren't any. As a result, the use of cable descramblers in the U.S. has been banned.

Likewise, using a file sharing program is meant to share files. Most of the files being traded with them are copyrighted materials, or derivatives thereof. These are not ordinarily found on the internet because it is (or in some cases is going to be) considered illegal to freely distribute these. Thus creates a demand for a peer to peer file sharing scheme. Is Gnutella encouraging the transfer of copyrighted materials? Almost everyone would have to agree yes to that. We are waiting for the courts to make an official ruling on whether it is legal to trade music on the internet even though it is copyrighted.

Gnutella is a wonderful tool that can be used to share wealths of information and knowledge, but unfortunately, many people are infringing established copyright laws. Luckliy, Gnutella is still in its infancy and is not attracting all too much attention yet. But later on, there's a hefty chance that Gnutella will be deemed illegal or banned altogether. But, as they say, only time will tell.