Would you follow "Terminator 2" on Twitter? No, you'd just get random "Have you seen this person?" tweets from someone with a T1000 avatar.
On Facebook, yes, I "liked" Terminator 2, and as a result will end up seeing advertising related to this in some way. I liked the Lord of the Rings books, or Tolkien, or Kanye West, but would I really want to follow Kanye on Twitter? Not so much. I love hockey, but do I really want to follow my team's Twitter feed? No.
And you talk about real-time content, maybe you misunderstand how Facebook can be used. I have an Interest List titled "Photography", I click on it and see all updates of every photographer I follow. Same for Music, etc. Twitter is a joke compared to this. It has nothing that Facebook doesn't have, and FB has all of it better anyway in terms of how useful the data is from an advertising point of view.
And as you said, they can't even show their advertising without destroying the usefulness of Twitter (whatever usefulness there really is to it). The only thing Twitter really has is: keep the messages to 140 characters.
It would be funny if FB added a "Feebee" feature, which would just be posts limited to 140 characters. What now?
Facebook is basically the internet, in real-time, filtered to my liking/interests/needs. It's the clearest most useful picture an advertiser could have from someone. They could add a "where do you want to go on vacation" feature, people would write in the places, and bam, people get advertising they actually want for tickets or hotels. Twitter can't.