If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.
Consider the dynamic version of the EMH: that is, rather than "prices are where they should be," it's "agents who perceive mispricings will pounce on them, making them transient."
Then a person placing a dumb trade is creating a mispricing, which will be consumed by some market agent. There's an asymmetry between "there is no free money left to be picked up" and "if you drop your money, it will not be picked up" that makes the first true (in the static case) and the second false.
Well, that looks like an "offering to buy a stock for $1 more than its current price" scenario. You can easily lose a lot of money by buying things at the offer and selling them at the bid :-)
But let's imagine a scenario where everything is happening pre-tax, there are no transaction costs, we're operating in risk-adjusted terms and, to make things simple, the risk-free rate is zero. Moreover, the markets are orderly and liquid.
Assuming you can competently express a market view, can you systematically lose money by consistently taking the wrong side under EMH?