Carmy said:
Publishers have no right to ask for exclusive viewing when they can take six months or longer to reply to a query.
They have the right. Terms of submission. It should be spelled out before hand. If an editor objects to simultaneous submissions he should say so or he has no recourse.
Given the lengthy duration for feedback, disallowing simultaneous submissions is unethical, but the editor has a time investment in the work and to read and accept a piece that has just been contracted by another publishing company is disturbing. I can see their point.
If you submit and disclose that it is simultaneous then the editor can make an informed choice to invest time in your work. He can put it down if he wants. But this is problematic as well. What if they all put it down and you don't get read. I don't submit simultaneously to publishers.
It would be nice if there were a way to put your work in a place that editors trusted and could go and scope out new work; like a magazine for used cars. The closest thing is an agent. An Agent is reselling you. He has a time investment in you also, but I see him as a door to door salesman. Reading is a small price to pay for his stock. He doesn't encounter the same gambles that the publisher does. I've got no guilt with multiple subs to agents.