I agree with you that $1B seems optimistic for 2011, but consider also that the Mac App Store may increase the total number of apps sold, perhaps drastically. I

I agree with you that $1B seems optimistic for 2011, but consider also that the Mac App Store may increase the total number of apps sold, perhaps drastically. I certainly expect I'll buy more Mac apps when they're more easily discoverable, more easily managed, and one-click-purchaseable.