Ticketmaster's explanation of their captcha (definition) includes a one-sentence declaration of a visitor's rights:
Some people use automated programs to block other customers from getting tickets. To counteract this practice we ask that you type in the word before we put tickets on hold for you. You do not have permission to access this web site if you are using an automated program.
The Mob: "But I'm using an automated program! Nooooooooooooooooo!"