Copyright owners have fought copyright infringement on the Internet by bringing infringement suits using IP addresses to identify the alleged infringers. That tactic may be getting tougher to use following a case in the United States District Court for the Central District of Illinois. In VPR Internationale v. Does 1-1017, Judge Harold Baker ruled that VPR, a Canadian adult film company, could not serve subpoenas on ISPs to obtain the personal information connected to their subscribers’ IP addresses. See Suing Infringers by IP Address Gets Tougher
And that's how it's should be. IP addresses mean very little: they can be changed, people could be sharing/public connections, or someone could have unauthorised access to yours. There is no reason that anyone should be able to infringe on other's privacy or destroy people financially because of digital media.
I've never thought it was reasonable for a company to sue a person based solely on an IP address. Like the previous poster said, addresses are shared and some of the times it seems as though lawsuits are filed just so the company suing can hunt for more evidence.
Yes, IP's don't mean anything, for example my ISP has a dynamic IP which is used my many people on the same host I find myself banned on from websites for spamming, scamming. Which I never visited.