At some point they switched to a slightly different model where you would see the normal obfuscated answers with a request to log in at the top of the page, but

At some point they switched to a slightly different model where you would see the normal obfuscated answers with a request to log in at the top of the page, but if you scrolled down far enough, the answers would be there in clear text. They were certainly walking a very fine line, but Google seemed to give them a pass with this system for quite some time.