Were there the right number of musicians in the pit as noted in the program?
I used "Sinfonia" (which is what it's called, MTI calls it one thing, RnH calls it another) for the helicopter show. It is a wonderful piece of technology for small theatres that either don't have the budget for a real orchestra or the space. The downside is that it's kind of hard to operate. I know many people have their opinions, but it's a useful tool.
Yes, the musicians were properly accounted for.
I should have added that I've seen it used in one community theater production (so far) and I didn't object to it there. That was BEAUTY AND THE BEAST, and the music director sat there right in front of the stage (pit area, but no actual pit) "playing" it with his left hand and conducting the stage (and only a bass player and drummer) with his right. The thing sounded great, for the most part. Certain bits would suddenly sound a little synth-y, which served to highlight how good the rest of it was. And would the production have been what it was without that? Not at all.
He told me it was quite the challenge to learn and master. But master it, he did.
So, I don't object to it in these certain situations. In professional venues, though, with all the space in the world.....