Facebook is picky to crypto advertisement last time they totally banned any crypto related advertisement but now they changed it to the pre-approved method before promoting and for Google ads you can check this latest article https://www.cnbc.com/2018/09/25/google-reverses-ban-on-cryptocurrency-exchange-advertising-in-us-japan.html
ICO's, wallet and trading advice are still not allowed to use google ads and this only applies to regulated crypto exchanges, the ads will only appear in US and Japan as per the article said, so yeah the option is to go for bounty but these programs exist before the banning period so this shows it is effective provided that they have the right marketing strategy and potential.