Getting Quest, Hit Rat, All Part of the Game

If someone had said that hitting a rat with a stick was part of the game they might not be too impressed but once it is framed as part of a larger goal it seems like legitamate behavour. Rat > Zombie > Ogre > Dragon can be imagined. In this clip the notion of activity being part of 'the game' legitamises it. How did these players come to understand what the game was? How much does getting a 'task' help?

When teaching in MUVEs such as Seocnd Life we need to establish with students what 'the game' is so that they are motivated to act. How explict should the game rules be? Certainly not as tight as this: http://openhabitat.blip.tv/file/852575/