This video should be watched by all those who don't specifically have one biner for pro and one biner for rope on each of their quickdraws.
While I thought it was obvious and required minimal effort to do I have seen a few climbers in New Brunswick not care about this.
Watch the video until the end.
And the argument that it doesn't apply to trad is false. Sure you clip way less bolts with trad, but you still clip nuts, pins, bolted anchors and the occasional bolt...
http://dmmclimbing.com/knowledge/carabiners-and-potential-rope-damage/