Is there some 'defaults write' or other trick to tell OS X to never mirror displays? (Unless they're at least as good resolution as the retina display.)
I thought I had display mirroring disabled completely just from the 'displays' options. Every time I used one of the extra displays (projectors, TV) I regularly use, I got a them as additional displays, not mirrored. But today, giving a presentation, I attached another new projector, and it was mirrored. The horror! My desktop was left after that like my house would be after a robbery. I hate mirroring, because it squeezes the retina display into 640x480, and I have to rearrange all the windows back into reasonable sizes afterwards.