We all know that "free" is used 99 % as a lie.
It does increase the CTR, ok , it's not good for ROI , but still , it takes a place in the adsense against real and honest advertizers, and does increase the price of bids because of it ...
My opinion, is for google to be a bit harder about the use of this word.
Google doesnt have the time to verify the claims made by the advertisers. Nor is it expected to do so. High CTR with Low ROI=Loss of advertisers. I dont think any wise advertisers do that.
I never searched for free, nor am I keen on using FREE as a term in my own optimization processes. Whenever something free is required I have places to get it from without having to use "thisandthat free" as a search term. Leave it as it is....I don't mind.
ha, what if someone searches for a copy of the movie "free Willy". that'd end up in a disappointed kid, in case google forbid FREE as a search term....just an example.