Everyone that has responded in this thread thus far ought to know what UAC is and does by now. This has been debated on countless occasions.
Yes they got the messaging to us wrong, I blame marketing and over zealous security PM's.
The fact of the matter is that most computers needs an expert to maintain them, that is fine if you are a developer or computer enthusiast, but a general user finds it difficult. Foisting this upon billions of users is not commercially adriot - look at XP!
If you were in charge of a multi-billion product, and one of the chief complaints was
security prompts what would you do? Obviously that complainant is a fool, but it is better to sell the product (like XP sold in droves), and leave that individual under the control of AV companies. It is less complicated that way, and you have
less complaints - far less by the way.
If users get a virus or their security is compromised, Microsoft's response will be elevate UAC, you complained when we had it high, now see what happened.
This is an economical descicion, and totally, wholly incontrovertibly the correct one!
After around two and half years of market availability (since january 2007) that's not that bad, considering how entrenched XP is, and the negative image that Vista has. The reason Microsoft destroyed UAC is because of the whiney blogosphere, and the statistics
show me, that the blogosphere has much less influence on the market than they think they have.