It looks like Microsoft is recognizing how interrogating the User Account Control (UAC) in Vista can be. They said
There are a LOT of UAC elevation prompts in Feb CTP and still more than we would like in Beta 2.
They said that their goal is to make the UAC prompts pop-up more after you install Vista and then have them learn from your choices. This would mean after a few days it would only be prompting you to perform such tasks as adding new software.
While using Vista Beta 2 I chose to disable the UAC because it would prompt me 10 times to perform some of the simplest tasks (a little exaggerated but it felt like it was that bad). If you want to see how bad it is then check out this gallery that demonstrates how it takes 7 steps to delete ONE shortcut.
Maybe Microsoft is trying get this UAC thing under control before they release Beta 2 to the public…hopefully.
News Source: Vista User Account Control Blog