There is some speculation that this might be an attempt by Blizzard to thwart the release of Warhammer Online, which is set to come online next Thursday. Warhammer has received some mixed reviews, with many comparisons to World of Warcraft, including one by Michael Zenke of our sister site Massively.
Nonetheless, those that have received keys are enjoying the thrills of the beta. New levels, the Death Knight, and servers crashing a few times an hour. Good times had by all!