Bungie have announced that the Halo: Reach multiplayer beta that is set to begin next week (May 3) will end as soon as May 19. A bit of a surprise given the amount of marketing the beta has been given and that it is meant to push Halo 3: ODST sales (you need a Halo 3: ODST disc in order to play the beta).
Learn more about the beta in Bungie's beta guide.