The solutions given is not entirely valid. I have an Amazon prime membership and I use it for the streaming video. You have to be logged in to select and play the videos. My sister does not have my Amazon password and I have One-Click turned off but this has no bearing on the digital content because it is all set up to be one-click even if you have one-click turned off for your account.
So, it is easy for anyone to use the mouse to stop the playing video and start making purchases at will using the one-click buttons. This is what happened to me and I was unaware of the distinction between the one-click settings for my account and how the digital content being set up exlusively with one-click.
I got on an online chat with an Amazon CR to see why my sister was able to purchase a video with one-click when I had it turned off and the CR went to verify my one-click settings were off and then came back and said it shouldn't happen again so while we were still in chat, I tried it again and of course I was able to purchase a video with one-click. The CR was surprised it worked this way and agreed that it was wrong to be set up like this with no way to guard against unauthorized purchases.
It only takes a few seconds to stop a video and click on a button to purchase a video.
If I don't explicitly log out of my Amazon account by clicking on "My Account-->Sign Out", then (even after a browser restart) anyone running that browser on that computer, can buy videos and kindle books on my account. A major security hole.