Apple - Removing spotlight icon from menu bar persistently
This works at least up to 10.9.2.
To disable:
sudo mv /System/Library/CoreServices/Search.bundle /System/Library/CoreServices/Search.bundle.bak
killall SystemUIServer
To re-enable:
sudo mv /System/Library/CoreServices/Search.bundle.bak /System/Library/CoreServices/Search.bundle
killall SystemUIServer
There are a few apps that can remove the icon for you, I used Bartender to check it works in Mountain Lion:
It will even get rid of Notification Center if you so desire ;)