Site administrators use CAPTCHAs to prevent automated scripts from performing certain functions, such as creating an account, sending email to a distribution list, or participating in a discussion thread.
That's fine, as far as it goes. But, frankly, I'd also like to see certain people on the Internet prevented from doing certain things. You know, like: logging onto the Internet.
And so, a modest proposal: Internet Access Captchas, built right into browsers, designed to greatly reduce the overabundance of youtube commenters, Facebookers, and Twittererers.
Here is my prototype: