sparrow
To prove that you are not a robot. It's annoying at first, but then you won't have to do it everytime.
Patricia
To make sure we aren't bots.
y
Every answer is a bit too much,
marty
They can charge more for advertising by showing the advertisers their ads will be seen by real people. They'll say it's for the benefit of the users to limit backlash.
Nerdy
There were bots at one point advertising and abusing the format here.