ThinkMac Software - Blog:
In the accessibility control panel Apple thoughtfully made all the text huge and bold to help people with visual disabilities. In the Time Machine preference pane they randomly decided your sight might be going a bit so they stuck in a giant on/off button. I'm kind of disappointed you don't have to flip up a little protective cover over the button and turn a key to activate it though. There should be flashing lights and sirens too, you know, just so you're sure it's on.