Read a book recently called Flashboys. A very good read, a rather murky incite into how investors get ripped off by the big Wall Street banks and the high frequency traders they are in cahoots with. Slightly worryingly, one of the tricks the HFTs use to tease market info out of unsuspecting investors, is to place a lot of very low risk bids into a market. The figures used was $100, I'm highly suspicious when I see such trading going on.