Oh, let's see...
Helium run a competition which they say is based on quality, but in actual fact, encourages churning where winning members were posting over 100 articles per week!
Helium members claim that winners of said competition act with integrity, but really all they did was paraphrase articles that had been previously posted or entries from Wikmipedia (and other such sources).
Caught. Red. Handed.
I'm sure you can point this kind of stuff out about all the sites though. (Ciao not rewarding the writing standards they set out, for example).