To return to my simplistic scenario, I see something publically accessable on the web. By your definition, copyright notices or not, it was authored and is therefore copyright. Though by that definition, my shopping list is also copyright. I find the information interesting and/or useful and make a local copy of that information. We could call this a "backup for personal use", no infringement.It's not "my definition". It's the definition of the Berne convention, a convention about copyright law signed by almost any country in the world, including the USA. It states that creative works are copyrighted, and that copyright notices are not required. Your shopping list is copyrighted if you can convince a court it was a creative work.
A friend comes around to my house and he views my local copy of this information on my machine. Is this analogous to watching a movie together? I would have had to have bought or hired the movie, thereby getting licence to view it. The aforesaid information came freely from the web. No one was paid. Am I going beyond the remit of "Personal use" by showing it to my friend?Whether or not you pay is not relevant whether you infringe copyrights or not. Though it may play a role if you get sued for damages. Even if you don't pay, the original author might lose money (say, by not getting pay for "ad hits"). I don't think you'd be breaking the spirit of the law by doing so. Note also there's no difference whether the other person is a friend or a stranger.
A step further, he rings me later and asks to view the information again, so I make it available (to him only for sake of argument) via some mechanism of communication. Am I or is he breaking the spirit or actual law by doing this?IMO, you are breaking the law. You're distributing a copyrighted work. It would be like faxing a book to him.
The next step of course is when he takes a local copy to his machine from my machine. What's the legal position now? Did he break the law? Would I be in breach A) if I knew he had done so? b) If I didn't?I don't think there's a difference between this step and the previous one.
I am no great expert on the law, but in the context of the original question in the post, I am struck by the absurdidty of the notion that information made freely available via the web can be subject to the restriction of "you may view this information freely, but only on this website".You can't tape a movie from a tv channel and give a copy to anyone who asks for it either without breaking the law.
Look, if you copy something from the net and make it available to others, you are very likely to get away with it. And even if you get sued, you might not have to pay damages even if you lose. But that doesn't make it legal, let alone ethical. What's so hard respecting the wishes of the author, and be conservative if you don't know the wishes? I certainly would like for people to respect my wishes and to not republish something I have withdrawn.