Web sites are different. Facebook is just one end of a spectrum of thousands, perhaps tens or hundreds of thousands of electronic destinations that come and go, and cost a few bucks to operate.
Regulations aimed at Facebook would potentially end up targeting every web site with user generated content.
However, I do sympathize on how much facebook is getting from its network effected position. It looks impossible to dethrone. Same for google.
I think the change has to come from how users deal with their own data. If you as a consumer had unlimited access to your data, you could potentially resell it to someone else, forcing facebook and the likes to compete on price. The key here is that the data has to be owned by the consumer, not by facebook itself.
With some meaningful regulation, we could put a stop to this overnight. The internet existed and flourished before this manipulative business model became the norm, and it would exist if we outlawed it. We wouldn't even need to outlaw it, just require explicit written consent to sell personal data.
Can you imagine the ramifications? Once you eliminate the lazy, tired, and frankly intellectually barren model of "make a mediocre service that sucks enough personal data from our users so we can sell ads against them", startups could go back to designing products that solve interesting problems that people are willing to pay for!
So what specifically would that regulation say?
In the end, all systems must have some form of regulator - from engines to code. If you are lucky, you create a governing function by playing engine forces against each other.
Demand is modulated by the ability of a pipe to supply fuel for example.
But most systems may not be with a self governable/equilibrium point. OR they may have one, but it is obviously repugnant to the purpose of the system.
It is then only logical, that a governing system is introduced to deal with the problem within the confines of what is human and practical.
The alternative is not necessarily something of value.
Or at the very least, more expensive.
Let's suppose a false rumor about you spread to hundreds of millions of readers on Facebook. You're shit out of luck and Facebook doesn't have to pay a dime. Germany however might change that with the new law.
Facebook is accountable to their users in the same way a farmer is accountable to his livestock.