Better get a new cup of coffee, a stream of consciousness follows....
Good point. I'll play devil's advocate though. (Terry must be getting to me)
For a more "sensitive" fish like trout in a spring creek barbless is the only way.
My experience with several different species of saltwater fish ( striper, blues, tarpon, barracuda, jacks & lemon sharks) leaves me to believe that a barb on a hook (a single hook) is the least of their worries. When you're slugging it out with an aggressive fish in the salt and it's using structure, current & leverage to fight the pull of your hook & fly line - you are leaving more than just the pin hole from a barbless hook in it's mouth.
That said, I do practice & promote C&R and, I do favor and use barbless hooks for the majority of my salt fishing.
However, there are a few spots I have been fortunate enough to frequent that hold larger fish and I am guilty of having occasionally left the barb on for these fish. In retrospect it's probably just a mental crutch for me.
My intention for the 2002 salt season is to fish barbless all the time - to really put a bow in the rod when I have a fish taking off with my line & backing. My reasoning for this decision is to increase my abilities as a fly rodder, reduce stress on the fish (does it really though if you're fighting a fish more "gingerly" because you have a barbless hook?) and for the ease of removing the fly from my person and anyone else unfortunate enough to be hooked by me.