Concrete example. In Tap my Katamari you only see ads when you choose to. You can watch an add to double the money accumulated when you where away. From time t

Concrete example. In Tap my Katamari you only see ads when you choose to. You can watch an add to double the money accumulated when you where away. From time to time the king will come with gifts, cash or candy, but ocassionaly the reward will be "watch an add for plenty of candy" or "watch an add to get money/tap for N seconds". This makes the person playing interested in watching the add, well, playing it at least while doing other things.