No adds. The entire NPOV policy revolves around not presenting any of our biases in our encyclopedic content. That's why users reveal their biases on userpages etc.; so we know what their opinions are, and we know what to be careful of when writing about. Ads, even Google Ads, are not neutral, and as noted above, a reliance on Google Ads would be disastrous when Google decides they want Microsoft to be defamed on the world's #1 online reference work.
Too many risks, not enough gain. When the Foundation is down on its knees and (literally) begging for donations, then we can look at it.