[mook]

"Just one button" led to Netscape 6 and subsequently Firefox in the first place. It's easy to miss the significant amount of user benefit from not having that one button, since it's a smaller amount of benefit per person across a lager number of users.

[azakai]

That's a fair point and I agree, there is benefit to not having more buttons on the UI. It's hard to know what the right tradeoff is, between the benefits of adding buttons and not adding them. There are good reasons to prefer both more and less.

In this case, data on user behavior indicated that it was worth adding the buttons. It's still possible that the data is imperfect somehow and a more optimal tradeoff could have been chosen. Still, I think there is good reason to believe the current data and decisions make sense.