The take-away point is this: there has been no ruling in either of these cases as to the relationship between an IP address and accused parties. Statements such as “IP addresses are not accepted as evidence” are simply false. Both cases were mutually dismissed, and both cases turn on arguments relating to who has access to someone’s Internet service. IP addresses are still evidence, but they’re not smoking guns (nor have they ever been). The idea that everyone accused of copyright infringement has merely to say “but, but the IP address!” to get off the hook is without merit. This has not been established in the slightest, and no judge has said this point blank, without qualification.
Read this article from Ars Technica