Prevent App Store from putting apps on the Dock in Snow Leopard In Snow Leopard, when I install an app from the App Store it automatically places it on the Dock with the "Keep in Dock" option enabled. 

Due to my poor mouse skills I've made the Dock immutable, so when I install an app from the store I cannot remove it! I have to unlock it, remove the app and relock it again.

It has happened enough times by now that it is starting to get on my nerves.

Any way to stop the Dock from automatically keeping new items or  stop the App Store from putting them there?
The app is added to the dock by manipulation of the Dock's preference file, then restarting the Dock, thereby bypassing the contents-immutable lock. To counter this, you can lock the Dock's preference file:

chflags uchg ~/Library/Preferences/com.apple.Dock.plist


Note: I don't have Snow Leopard to test this on, so keep backups, etc.

Undo with:

chflags nouchg ~/Library/Preferences/com.apple.Dock.plist