I've seen this sort of behaviour modification with online competitions, especially on facebook. E.g. The "like, comment and share" type competitions. I would argue many of these competitions are dubious as there is no oversight and I've read enough about fake ones to take the view that I would rather not go near any of them. But so many of my acquaintances slavishly follow the instructions in the hope of winning a gift card or some other piece of tat.

Actually facebook and its more savvy advertisers and posters seem to really good at this sort of thing. The amount of people, whom I would consider educated, who share freebooted and farm-produced content surprises me.

Similarly there is a UK Fishing forum that requires you to accept and open promotional emails from the store that owns the forum in order to be a member. I'll happily throw in a few quid a year to support a useful forum, but going through the hoops of having to open marketing emails to reactivate my membership is just too much.