Can I force Mac OS X not to complain when a volume is removed without first unmounting it?
If you don't mind losing notification center, you can disable it.

To disable NC, thus stopping the removal message, type in:

sudo defaults write /System/Library/LaunchAgents/com.apple.notificationcenterui KeepAlive -bool false


Then, type in 

killall NotificationCenter


To re-enable it, type in:

sudo defaults write /System/Library/LaunchAgents/com.apple.notificationcenterui KeepAlive -bool true


Keep in mind, besides disabling this message, it will disable ALL messages.