I've argued this case to friends and in writing before. There is really no way to link an actual person to files that appear on file trading services. In addition, I argue that just becasue you have files available on a file trading service, you aren't doing anything illegal, if anything it would be the folks downloading them.
From the article, after the RIAA gets a persons name from an ISP that was tied to an IP address (often dynamically) and often shared via wireless routers:
Once the RIAA has a name, the RIAA brings a case against the individual identified. As Beckerman points out, at this point, the evidence is inconclusive. "At most, they can say that someone who might somehow be associated with that IP address might have made some files available. But they certainly don't know that the defendant did. All they know is that the defendant wrote out a check to the Internet provider."
However, this vagueness does not stop the proceedings. The RIAA's preference, Beckerman says, is "to extort a [cash] settlement." If an individual resists, the RIAA brings a federal suit against him, which few individuals can afford to defend against unless they can find a lawyer willing to work for free or for a nominal fee. "You'll notice that you'll never see a big law firm in that category," he says. "The big law firms are like any big corporation -- they need to make a profit. They would be interested in representing the RIAA, not the poor people who the RIAA are pursuing."
This is sad and we should be aware that this is happening. We should at the least donate some money to the EFF and the Free Software Foundation (who has a legal fund up) :
Brown also mentioned that people can donate money to the cause through the FSF Web site, or by sending checks earmarked "RIAA Lawsuits" to the FSF.