Countless times I've set my audio levels across multiple clips using the "Set Level On Track - In/Out" command, only to later discover to my horror that I'd had my marks set wrong and either set the level for the track globally, or from the in point all the way to the end of my timeline.
Over the years I've destroyed enough mixes this way that I'd really like to see an option to have Media Composer prompt me with an "Are you sure?" any time the user tries to set levels globally, or with an open IN or OUT point.