...and then, if your scheme works (which, as others have pointed out, would take a miracle, and a very carefully chosen market that's not handled the way most o

...and then, if your scheme works (which, as others have pointed out, would take a miracle, and a very carefully chosen market that's not handled the way most of the big ones are), both you and your friend go to jail for market manipulation, which would be rather simple to prove - there's almost no reason you would ever want to sell something way below the best bid, so you're without the usual excuses that market manipulators use to justify manipulative trades ("uh, my analysis showed that the 26.5 day moving average crossed the 100 day low, so I bought, but then I noticed that the pork bellies volatility was higher than usual, so I sold a few seconds later, because that's the way my strategy works...").