You're not overriding the law if you're not cracking or phishing for their password. If you state in the terms and conditions exactly what you are going to do, you are requesting their consent before doing these actions. Cracking and phishing is done without the user's consent, and that's why it's illegal.
If the user provides their consent by taking the quiz and provides their login credentials, but fails to read exactly to what they're consenting to; then the user is negligent and not the service provider.
Credit card companies tuck away all sorts of hidden fees in their terms too. It's perfect legal for them to do so as long as it's in the terms. The cardholder however rarely reads these terms, but they still give their consent by subscribing to the credit card.
If a bank was charging hidden fees without disclosing them in the terms, then it indeed would be wire fraud. However if the banks disclose the fees in the terms, then it's perfectly legal. The same applies with obtaining someone's login credentials via consent versus obtaining them via phishing or cracking.
You would be correct however that one can not sign a contract to be murdered or enslaved. But whether you give consent or not, murder and enslavement is always illegal. However sharing passwords is not such a clear cut case. As long as the password is to your own account, you can share it with whomever you wish.
