Speaking on behalf of Twitter, we do embrace the idea that our users should know who is paying for the advertising, especially when it comes in the political context.
In the conversations we've had, and in how we are communicating with governments around the world, we recognize that the online environment is different and that, for instance, Twitter is a character-limited platform. It used to be that we had 140 characters. Just recently it was bumped up to 280. Your standard political disclosure language is hard to squeeze in there.
The other complications are often very short videos.