The dragnet spying that forms the core of social networks' business model ought simply be illegal. It's disgusting and tremendously dangerous. That'd help a lot—by destroying some of the companies, and removing many of their worst incentives.

Also, they shouldn't be able to launder responsibility for editorial choices by saying "an algorithm did it!" and hiding behind laws meant to protect email and IM providers and web hosting companies and ISPs and such.

I expect that combo'd fix a lot of problems.