I see the incentive on PUT like affiliate marketing done right. Farmers want people to put their data on the network. Developers create apps that incentive user to put their data in. Farmers are happy because they get more data and developer gets rewarded for putting the data in. Users get value out of using the app because since they are paying for each PUT request they would not do a PUT request that doesn’t bring them value in return. The interest of everyone align perfectly. It doesn’t require a reputation system, doesn’t require any proof of human or proof of authorship. It’s a simple and elegant solution.
Of course many developer and content creator won’t be able to make a living off this revenue alone, but for them there’s gonna be so many options to choose from. I think that once the safe network has launched, MaidSafe and the SafePod devs should concentrate, among other things, on developing all kinds of income scheme: pay wall, subscriptions, pay per time used, crowdfunding, patronage, advertisement (yes, yes), etc.