I think the social media giants are right in banning ICO related ads. The truth is that there are tons of projects that are scams. There are teams with people who have no past credibility, projects that don’t be even have a minimum viable product and products that don’t even solve real problems. 

If you look at the dotcom boom, there were tons of websites and companies with insane evaluations. Companies with no customer base or revenue.

An approach ICO's could take is creating content that educates people in a way people can understand and connect to the mission. They can also leverage authorities in the crypto space and collaborate with them.

I honestly don't think billboards are the best way to market, but it doesn't hurt.