I am not really sure if this counts as a scam or not...
One of my clients was approached recently with a print out of the w3 validator which had a bunch of errors on their website.
They have been quite persistent that they must get these errors fixed. (For $350)
Anyway, I won't name the company but this is just a heads up that w3 compliance is not a requirement. If you have any doubts then put google.com or even geekzone.co.nz into the validator and see what results you get.
Freatism, I can fix the gz errors for $350 for you.... promise.... ;-)