I used to laugh off the manipulator hypothesis as well but over time accepted that their is validity to the fact that someone with a lot of money to throw around manipulates the market for shits and giggles. My personal opinion is that they are doing it to screw miners out of making a large profit to reduce competition in the big money region (north of 50k coins).
I laugh it off because the name completely neglects any rational psychology.
It's not manipulation, it's trading. I put up and remove bid and sell walls all the time too. The only difference between me and them is that they have way more capital than I do.
It is trading if you want to hold some bitcoins and you buy them, or if you have some bitcoins and you sell them at the current market price. Or maybe even throw in a set price for your bitcoins.
It is manipulation when you put up bid walls (as the manipulator does) to try and make other people buy or sell bitcoins. This is manipulation because he is trying to show that there is lots of demand for bitcoins, when in reality he just removes these bitcoins as soon as the price starts dropping.
I am sure you get my idea. He is playing on the psychology of others.
EVERYONE plays on the psychology of others. I put up buy and sell walls too. I simply don't have enough capital so the influence of my orders doesn't have nearly as much psychological impact on the market.
What I'm saying is that the only difference between the guy or group of guys who place large bid/sell orders and everyone else is that they have capital and their bids/sells are noticed. If you argue frequency, I'll argue back. I sometimes adjust my bid/sells 10 times in an hour depending on market volatility, but far less (if at all) when volatility is low. This reflects the movements of large bid/sells on mt. gox -- they are more frequent when volatility is high.
It's also kind of moot to talk about wanting to make people buy or sell bitcoins -- it ends up back at the money differential. When there is a panic buy or sell, people buy and sell. Every buy in a panic buy can be seen by others on Mt. Gox Live and it adds to the event psychology. The only reason it isn't as likely to make the market move is because the majority of people have less money.
But then again, the
sum of all people with less money than the "manipulators" could also said to be manipulating the manipulators! That's what happens in panic buys and sells. Everyone buys or sells because they 1) Want to get in on the action and 2) Want the market to move in a certain direction. This then 'manipulates' what the 'manipulator' does. And, the reverse is true for the 'manipulators,' too -- 1) They want to get in on the action and 2) Want to make the market move in a certain direction. And in that order.
It seems manipulators are simply guys with loot. Next you know, the 'manipulator' will be statistically random and everyone will panic and cry, "He's so ruthless! Nobody can figure out what he's doing! It appears his actions look like everyone else's! He's a genius!"