When a commercial interest is providing educational material, what guarantee is there that the material will not be manipulated for the purpose of profit? Wikipedia has maintained a great reputation for providing knowledge and having clear rules for debating facts and guarding against commecial interferance. There will always be disagreements among people, but a different element is introduced when a commercial enterprise becomes the provider.
The new Google Knowledge Graph is clearly a threat to wikipedia. Starting first with basic facts, Google could become the "go to" place for information ahead of wikipedia. Will this "knowledge" then be distorted with ads? Often right now telling the difference between and ad and an organic link on Google. Do we want a corporation becoming the leading source for knowledge when it also serves up advertising? Could some information be changed to serve corporate interests?