Spoof orders, or placed market trade orders that are not actually intended to be executed, are part of the rampant manipulation of traders on cryptocurrency exchanges. Trading into your own buy or sells is also illegal in the regulated financial markets, and it is suspected that this behavior has become more rampant in order to help Bitcoin price manipulators cut potential loses from their dubious activities. They also serve to sway trader behavior with massive sell and buy walls which are suggested to be the work of an individual or group, perhaps even the exchanges themselves going under the pseudonym of Spoofy.
Article on Bitcoinist