Re: What happens if...
It seems pretty simple to me.
If you are authorized to access a given system the owner (or their authorized agent for such purposes) of it will have provided you with a userid and password of your own to facilitate that access, if they haven't, or won't, then guessing someone else's account details or persuading them to give them to you is the same as any other form of hacking in - it's illegal because you have not been granted authorized access and you quite rightly run the risk of being done for it. Where I work corporate policy is also very clear that you'll also be invited to seek exciting opportunities outside the company.
Using a spouse's or friend's account details to access their computer should also be fairly straight forward - if they own the computer/system, have given you their account info and told you you can access the system using those details then they've authorized you to log in using those details - if they didn't want you to do that they should have created a separate account for you or told you you can't have access. If you then log in using their account without them authorizing you to do so, then once again you're on the dodgy side of the law (not to mention the relationship). I have a separate account on my wife's personal laptop and I also know her login and password - but I still check with her every time if I need to log in as her to look at a problem - just because I know more about computers than she does doesn't reduce her right to whatever level of privacy she desires.
Even giving a family member the details to your bank cards is covered - the T&Cs for these (and any of the numerous company ID/access cards or tokens I've ever held) invariably make it clear that the card or token remains the property of the issuer - in other words, you as the user are not the owner and therefor do not have the authority to delegate use of that item.
Simples, really.
Biting the hand that feeds IT
