Traders were and are probably still doing that with FNMA.
It's a good way to lose a lot of $$$ in a short period of time.
The stock collapses, so the trader wants to get out NOW and sell. They go with a market order sell, but it doesn't go through for several minutes. They end up losing more $$$ and complain to other traders about their misfortunes.
That's why I always use limit orders. Better safe than sorry.
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