I hate CAPTCHA
The technology used by some web sites, most proeminent being Yahoo, in order to differentiate between humans and spam bots is at least unnerving. Each time I want to join a discussion group, I have to use my imagination, because the difformed words I should be reading are really hard to read.
But I learned some good things. First of all, people developed programs that read those words in 75-80% of the cases.
And then, while visiting the demos on the CAPTCHA project website, I saw this:

I can’t find the word "good" in the picture. It wants me to imagine words! That’s why I received so many errors on Yahoo! Groups.