Three excellent and well articulated points, thank you. I agree, but would have taken three times as many words to make the same points!
Thanks for that! Having received that encouragement, I'll go on a less succinct rant.
I'd also like to add that although I use playback very, very rarely, there have been occasions where I've asked others in the vicinity if they mind if I use it, and have been surprised to receive enthusiastic encouragement. I've never had a refusal, but that may be because I've been very careful about guessing what the reception might be.
On an almost unrelated note, I've been surprised how many people are very unfamiliar with the calls of common birds, and who have been very grateful when I can quickly find the call of a bird we're looking for, or which I've just heard, and play it to them (not to the bird) so they know what to listen for.
I assume this unfamiliarity has come from the difficulty in accessing bird calls until recently. In this country at least, calls were only available on cassette until perhaps10 years ago (guessing, I came in after the CD era began). This meant carrying large sets of tapes around, and then fast forwarding by trial and error to the species concerned. It was only for the truly dedicated.
Even after CDs became available, only the dedicated bothered to go through the process of changing the CD and looking up which track number to play. Then people started ripping them to mp3 and putting them on their mp3 players - iPods, etc. Still very hard to access because mp3 players were designed for playing whole albums, or random selections, not jumping straight to track 537 of 1093, let alone finding a track by name (if you'd even managed to name them all).
It was only the introduction of mp3 playing phones with keyboards and touch screens that finally let people find the right track quickly without effort, on a device with a built in speaker. I'd say this happened only in the last 5 years, and I've noticed that it's becoming increasingly common to find that people have all the local calls in their pocket. The release last year of an Australian field guide app with lots of calls, for a fraction of the price of a a full set of call CDs, means accessibility has exploded here.
With this sudden availability will inevitably come vastly increased use of playback. I'm of the opinion that it simply doesn't matter whether it's harmful or not, so long as very few people are doing it. Soon, if not already, lots of people will be doing it, so it will matter a lot.
There are very few guidelines for the uninitiated about playback, other than "Just don't do it", or "Be careful about it". I guess birding groups baulk at the idea of giving instructions for using playback, but these might no longer suffice.
Summary: If you think it's bad now, wait till not just every single birder has playback at their fingertips 24/7, but also lots of vaguely interested members of the public. What can be done?