It probably wouldn't have a effect, but because these things are impossible to measure, there's no way to know for sure. It seems clear that even the perceptio

It probably wouldn't have a effect, but because these things are impossible to measure, there's no way to know for sure. It seems clear that even the perception of possible bias created by ad revenue is of negative value to Wikipedia. It's possible these effects are small. However, as an organization, they've clearly decided that the total costs of advertising outweigh the benefits.