The company had previously said it was preventing cryptocurrency accounts from interacting "in a deceptive manner," but hadn't gone so far as to institute a ban.

It's not shocking that Twitter would crack down on these ads. Many initial coin offerings are speculative and dodgy, and in extreme circumstances are outright scams from fraudsters who spend contributors' money on themselves. Tokens, wallets and exchanges often tend to be volatile, too. As with Facebook and Google, Twitter likely doesn't want to risk either the bad public image associated with flaky cryptocurrency ventures or the possibility of enabling financial crimes. You may not see the social site allow most ads until there's a stronger set of rules protecting would-be investors.