Why do you assert that it "most likely occurred" because of this?

Do you have any data?

I doubt they would be that petty, if it became a common thing for Google to apply the banhammer for mild critiques of their business practices that would cause irreparable damage to the brand.

We would all be trying meta-search engines that compared different result sets. We would be back in the late '90's trying to figure out which search engines were reliable and honest. (anyone remember Dogpile?)

Except that now it's all incumbent monopolies and high barriers to entry.

If nothing else this should give a boost to small outfits like DuckDuckGo http://duckduckgo.com/?q=site%3Aroughtype.com