Really? I completely disagree with this. I would never go into a game blind. I would at the very, very least expect to know the geography, basic history and culture of the game I'm going to play in. There have been numerous polls on En World talking about which types of creatures don't get used in people's games. The most recent one had Fey leading the pack with a few others close behind. If you're intending on running a campaign based on, say, the Faerie Queen, then it might be a good idea to run the idea past your players.