It is possible to generate a random symmetric-encryption key on your computer, put it on a USB drive (or even a piece of paper), meet a friend in person, give them the key, and subsequently use the key to transfer unlimited amounts of copyrighted material between the two of you through the internet.
> have no idea what "breaking and entering" has to do with this.
That should be clear now. The only way for others to obtain the decrypted contents of the transmissions between careful friends in the above situation is with some kind of breaking and entering. The fact that most people don't do this, most of the time, is irrelevant; it is important that we are able to do it if we need to.
The only way to really prevent the above scenario is to make it illegal to do some of the above things: to own a general-purpose computer that won't snitch on you, to meet a friend and exchange something secret without having your person searched, to send encrypted information through the internet, to live in a place that doesn't have cameras watching to see if you're viewing illegal material, etc. (I suppose paying a reward to people for reporting on their neighbors, friends, and family for possessing or distributing illegal material might be reasonably effective too.) IP law is only really enforceable with a police state.
> It's simply because you left that information there with an implicit understanding that that information would be used only for purposes that you agree to.
Actually, sometimes the understanding is reasonably explicit. For example, Gmail has a privacy policy. It says, "We do not share personal information with companies, organizations and individuals outside of Google unless one of the following circumstances applies: [with your consent, with domain administrators, for external processing, for legal reasons]", and later it says, "If Google is involved in a merger, acquisition or asset sale, we will continue to ensure the confidentiality of any personal information".
A website's terms of use take the form of a contractual agreement between the user and the company; the whole thing is a bit laughable, since usually the company doesn't have a human negotiating with the user and the user doesn't read the policy, but the subsequent exchange of valuable services for valuable data can be construed as grounds for some kind of enforceable agreement, and the words of the ToS should at least be a first approximation to what that agreement is. And people justifiably feel violated if someone ... violates the terms of a contract under which they've given up valuable items.
> IP and privacy are both flip sides of the same coin.
Nope. In case you're wondering, if a Google sysadmin decides to publish my emails to the internets, I will be offended and expect him to at least lose his job, and I may have some complaint against Google, but I do not believe I have the right to subsequently prevent anyone else from making copies and spreading them around; they were not bound by any contractual agreement with me. And I expect that, in practice, my emails will probably remain private: the few who could read them (Google employees, the NSA) risk negative consequences (firing, bad press and Google fixing their security breach) if they do anything to reveal they've done it.
By contrast, those who favor IP and use it hope to make exchange-contracts with thousands or millions of strangers, each one of whom is expected to have intimate contact with the information. Reliably preventing any of them from sharing it requires the active intervention of the law and a lot more.
> And they, similarly, feel violated when people access it without due recompense.
It is unfortunate that IP laws and rhetoric have given them such an expectation. I understand some people feel violated when gay people get married in their church or when someone buys a copy of a holy book and burns it. However, to let their feelings control the force of law would have unacceptable consequences for human freedom.