LOL

I faced similar ones in the past and was also wondering if it's just coincidence.
BTW you know nothing about captchas

if you haven't faced Rapidshare's ones in the last period of that site great popularity:

It wasn't about checking if you're human, it was more like test of your skills - survival of the fittest

The worst Captchas are those showing you nine photos and ask you to pick related photos. That one was really survival of the fittest.