What you are talking about is more a problem for a site like Wikipedia which ends up being quality limited because the quality of its users. Stack Overflow is m

What you are talking about is more a problem for a site like Wikipedia which ends up being quality limited because the quality of its users. Stack Overflow is more about finding a needle in the haystack. Which is a scenario less susceptible to those problems since it generally requires experience, rather than expertise, and can be validated by the people involved. Which is also why it would be counterproductive for SO to not manage the size of the haystack.