Nintendo: Publishers set the play limit on Wii U demos
With the release of Rayman Legends demo on the Nintendo Wii U eShop, now seems like the perfect time to address the play limits on the Wii U's demos. Demos on the Wii U from Nintendo's eShop are limited to a certain number of uses. For example, the Rayman Legends demo has 30 uses. After you use up the demo's limit, you get the message, "This demo can no longer be used. View information about the full version in the Nintendo eShop?" You are then redirected to a page where you can buy the full version of the game.
According to Eurogamer, who asked Nintendo why there were limits on games and why the limits varied, a Nintendo spokesperson said, "Each publisher has the opportunity to decide how long demos will stay on the eShop, and how many times consumers can play them before they expire." That demo limit is also implemented on Nintendo handheld, the 3DS.
I don't really see the big deal in there being a limit on how many times you can play the demo. If you're playing a demo 30 times, you obviously like it, and if that's the case, you should purchase the full game. Who is playing a demo 30 times anyways? And while there's no play limits on demos for the 360 and PS3, there are trials where you can only play for an hour.