The document now leads to a 404. I guess somebody heard you ;)

Or AI learned of the off switch and executed the off switch on the file.

Wouldn't CAPTCHA be useless against a sufficiently smart AI?

I think the captcha would be kind of useless, but the paywall might be able to prevent any issues in itself. Unless AI start being offered credit cards in the future, it's unlikely it'll be able to pay to get past one. So what's left? Trick some poor human to let it in?

On the other hand, a real life robot has a fairly easy to use off switch. It's called 'destroy the robot with copious amounts of firepower'.

I imagine an AI with internet access could manage to find a few credit card numbers...

It doesn't take a superintelligence to reason that the less intelligent people who created you probably took out some safety measures in case of you going rogue, and to figure that one of them is probably a kill switch. It's just the obvious thing to do. The AI doesn't need to stumble across past vague theorizing in order for this to occur to it.

if current algorithms can kick our butts at chess, an eventual future AI would pretty much know what we would do before we think of it

If the thing is anything evolving from an internet, it would surely know how to shut off or have a strong incentive not to. We would have, but then you don't want the plans known. I see.

Then the AI would pay someone to solve the captcha so it can read about its kill switch.