Not all your users are the same. Some see their output stream as a work product. Something they care about, learn from, put love into, and use it as a way to gather ideas from others. For some people this will be considered enough of a product that they want to be paid for it.
I know that may sound audacious, but it's actually pretty conservative. I think when all this shakes out these people will be like NBA players. They will be the ones people show up to hear from. They won't necessarily be the celebrities from the TV world, much as YouTube has created a generation of celebrities that now play on TV.
Twitter, especially, should be trying to identify these people and do deals with them, that pay them money, and possibly even give them equity. Golden handcuffs. And Google, looking to gain entry here, should be raiding Twitter's stable of talent, before Twitter is even aware that they have such a thing.
This is one that I am totally 100 percent sure of. As sure as I was in 1978 that there would be software products that people would use. That was considered pretty radical at a time when programmers all took jobs in research in big corporations or in the defense industry.
Another take-away is that there will be a market of tools created for these people. Don't think of hamster cages, where you provide the service for free and then mine the data. This data is worth too much for that approach. Think of it instead as a great gym for a world-class athelete.