But what benefit does that actually have? People aren't going to remember this interaction or learn anything, they're just to be annoyed at having to come up w

But what benefit does that actually have? People aren't going to remember this interaction or learn anything, they're just to be annoyed at having to come up with that number. They might even put off the transaction. I would be in favor of restricting the use of market orders by non-professionals during any time a market special rule is in place (circuit breakers, Rule 48, etc.) However, I think allowing them during normal market operation makes transacting easier for investors, which is also a good thing.