Tangentially, see In 2017, Google removed 3.2B ‘bad ads’ and blocked 320K publishers, 90K sites, 700K mobile apps (TechCrunch)
"In June 2018, Google will update the Financial services policy to restrict the advertisement of Contracts for Difference, rolling spot forex, and financial spread betting. In addition, ads for the following will no longer be allowed to serve:Financial Services: New restricted financial products policy (June 2018) - Advertising Policies Help
- Binary options and synonymous products
- Cryptocurrencies and related content (including but not limited to initial coin offerings, cryptocurrency exchanges, cryptocurrency wallets, and cryptocurrency trading advice)"