I responded to another comment here about it. WoW and other MMOs would be my choice – but to make it any fun you’d have to rewind the whole world. Not only get rid of wowhead, wowwiki, raider.io etc., but get people to forget they ever existed, forget how to do data mining so effectively. Also get rid of streaming and video sharing services so that you had the chance of discovering things on your own. You wouldn’t be the first, but you wouldn’t know that.