It is basically like Smoking Mils the Runescape clan that maniuplated prices of items in game. One minute a certain potion is worth 5,000 gold each and within two days it is up to 7,800 each and they already sold and dumped it all. The trick they used was having people buy in and then swear everyone to secrecy and it worked for them, the inside buyers knew what the new item was everyone would buy and they silently bought items for a few days and then made a "HUGE ANNOUNCEMENT" on their forum for the general public to see and the first average people to get in on it made some nice bank and the late comers lost a ton.

Bitcoin could be done this way also but its real money you are doing it with and most people didn't put real money into Runescape, they just played for awhile. So to do this would be very risky to crash the price and make it go way back up.