I think you underestimate how much advertisement would influence such a website. There are very strict content rules with most advertisement networks and threa

I think you underestimate how much advertisement would influence such a website. There are very strict content rules with most advertisement networks and threading over those will severely limit the income from ads as those that run advertisement often do not wish to be associated with various content. Consider what happened to TVTropes, which at one point decided to remove articles that dealt with a variety of sexual subjects as it was very bad for their advertisement revenue that the articles even existed on their website. If Wikipedia become dependent on advertisers, it would have to tailor it's content to accommodate them. Of course, it's content also influences the number of donations they receive as it is.