The landline doesn't really matter. The assumption is that most people use wireless Internet at home. Wired landline to the router/modem, then wireless to the computers. If it's not secured, anyone can use the connection. Just drive up to the place within wireless range, connect, and there you go. Kind of like what Google does.
-Renegade
It does matter, and I asked my question for a reason, because chunks of Americans don't have wifi. So you get a question like "do you have a wifi set up?" and if the answer comes back "no", where does that leave you? I turned OFF my wifi because I do all my computing from my desktop, so why do I need a wifi again if I only live in one room?
Nice Chewbacca attempt though.

So I repeat, if someone has no wifi, is a landline IP address "close enough" to determine a user? Because except publicity "Streisand" problems aside, this isn't very far from saying "you watched a tv clip on youtube, and you had Reasonable Doubt that Cucumber2265 wasn't an authorized source, here's your fine."
Addenda: What I am getting at is that if you make it the *user's* burden to try to source materials, you get a whole lot of trouble reeeeeeeallly quick. And all because we can't separate copyright into "types". Look at the pictures we like to post. Look at the "recommend videos" threads. Basically, look at "Sharing" which is all of Web 2.0. I'm getting chills seeing the conflicting forces here. Going all Grade C Prophet, I remember very little of anything, but I distinctly remember about 1999 and 2000, at the Dot Com boom and crash, Y2K, early 9-11, that "all the tech has been done except minor updates on features." So even skipping the whole Mobile movement, and a couple new drugs, I was right. Once there is no world class innovation left, "we all just sit here staring at each other getting bored" and that's where we are now - "bored" = "IP lawsuits." ((Look at the accidental pun, Internet Protocol address lawsuits to protect Intellectual Property. Or if Apple gets involved, iP. )
Extra Credit: Do you know how *hard* it is to source something? Most men like a little pr0n now and then. It's usually framed to hell and uploaded to 5 sites. Can you imagine trying to find the original creator of that? Or if that makes you squeamish, even the cat pictures are almost impossible to source.