I apologize if this belongs somewhere else -
Does anyone know why certain stocks will have moments where the trading price drops significantly, just for a moment, and then goes right back to where it was?
For example, yesterday, Tuesday the 20th, on this stock for SPY: (30 minute chart)
Looking at a 1-minute chart tells me that that entire drop occurred in less than one minute.
Someone told me that this is the "market maker" "pulling out the stops," implying that there is a person who arranges buys and sells who wants to punish people who have a lot of stop-sells on a certain stock, and who momentarily prevents higher-price buyers from being able to buy.
1. Is there a person consciously and actively doing this?
2. Why would he do this? Is there something bad about a lot of people having stop-buy orders in place?
3. Does/could this situation ever occur the Bitcoin markets? I imagine not since I don't think mtgox allows stop orders.