Too Much Gravy for High-Speed Traders

One good general rule is that it's harder than you think it is to figure out what's market manipulation and what isn't. Trading a lot, cancelling a lot of orders, putting in orders or doing trades on both sides of the market, trading a lot right before a close or fixing -- all of those things could be signs of nefarious manipulation, or just normal risk management. No single event or pattern proves manipulation. You often need to look for subtle clues to figure out whether a trade is actually manipulative