Actually Tommo, the answer to your question as to how it happens is quite simple. There were 400 oppies for sale @ 12c. Somebody put in an order for say 20,000 oppies at 12c which resulted in the 400 being sold into that larger order and the remaining 19,600 listed in the buy queue as the unfilled part of the buy order.
In this case the remaining 400 shares from a previous sell order and the new buy order for 20,000 shares came via the same broker so its an XT. Because lots of additional buy order suddenly piled in @ 12c the remaining part of the larger buy order isn't obvious but its there and with the price rising the person who did it may have to pay his $19.95 brokerage even if the remaining order is never filled. The price will be 15c afterall.
SSN Price at posting:
14.0¢ Sentiment: Buy Disclosure: Held