It's one form of Turing Test, as I'm sure you already know. I hate the ones that use distorted fonts because they are so hard to read.
I used to participate in a forum that ALWAYS had a Turing Test for SEARCHES but not for POSTING. What's up with that? I've never understood it.
Didn't know they had a "name".
I have a difficult time reading them

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic