I still can't figure out what captcha wants. When it tells me to select all squares with a bus, I can never get it right unless every square is a separate picture.
Captcha was implemented to stop bots and now they are so fucked up that bots are better at solving captchas than humans.
For example the captcha on this site (it's a google search proxy). It took me 4 tries and last time I checked, I was human. To be fair, they call it an intelligence check, so maybe that was the problem.