Reports are starting to appear indicating the Vista's activation program can be relatively easily hacked by a brute force attack. An article today in the Inquirer "Vista activation cracked by brute force" quotes Keznews which contains software and step by step instructions on how to conduct the attack. Keznews states the attack can take hours or days to be accomplished using only one PC.(on the main page a user states they got three keys in five hours). If you were to apply a cluster of PC's then the time becomes easily handled by criminals.
If this report is confirmed, it puts a very dark eye on Vista.