Just to show how absurd such practice is - if Mozilla wanted to do the same, they should intercept requests for Google.com and Bing.com, advising users to use Mozilla's search engine instead. I doubt Google would keep paying them if they did that though.
Which is the real problem with Mozilla being dependent on money from Google. Google can do whatever they want against Firefox, but Mozilla is very limited in its response because they can't risk upsetting Google too much.
