Sometimes I see the price moving up or down 20 cents, without a single trade happening, only people putting and removing orders, A LOT.
But when I see the trade history, there are so few of them that it looks the site is dead.
Someone know what is going on?
That's what happens when MtGox lets bots run the show. The bots are playing arbitrage with other exchanges. The other common thing to do is flood the order book and just as quickly remove the orders. They never get traded, but may influence less sophisticated bots into conducting a losing trade.
The lack of constant human oversight is often highlighted as a problem with real exchanges such as the NYSE. Bot trading is a bit out of control. Just today an article was published about a new Europe to USA Internet link that promises to shave 6ms off the ping time for $300M.http://www.telegraph.co.uk/technology/news/8753784/The-300m-cable-that-will-save-traders-milliseconds.html
Traders are salivating over the possibility of playing the arbitrage game more effectively than their competitors. It's all a bit silly really, but there's serious money to be made. My ping time to MtGox is 190ms. I wonder if bot traders have hosted their bots geographically close to MtGox's servers
I wouldn't be surprised if 11 September's wild price swings were buggy bots at war, manically trading between themselves. Either way the only real winner is MtGox. They take their cut no matter what.