You know what they really cant do that right now because crypt related ads comes from our searched history with you have a small indication of your previews search that is crypto related.
Also Why?
•We have this thing called cache or cookie in software definition.

•In my opinion it will not be banned but if in any case bitcoin or crypto related ads will ne banned, google will do everything to stop the ads.

So as of now I can't  see any reason of google or facebook to ban crypto related ads and ICO.