We don't need a great firewall, just Facebook and Twitter to get their fucking shit together. Also, there's more to charges this than just social engineering. They actually did hack voting commission data.
Even if you think the social networks should be trying to solve this problem (and some would argue that it's a hornets nest they would do well to avoid), acting as if they're being negligent or incompetent because they haven't figured it out already is a bit unfair.
If you're asserting that Facebook should say who's REALLY behind by the ads, you're basically asking for Facebook to hire a crack team of private investigators. Should they be responsible for figuring out that Nice Ad Buyers LLC is really a wholly-owned subsidiary of some other corporation, which some neo-nazi millionaire owns the controlling stake of?