Someone is playing ping-pong on MtGox. Ping is a transaction of a few bitcoins at some price X in the gap between the highest stable bid and lowest stable ask. Pong is a similar teansaction at a price Y some 5-10 USD below X. Each transaction seems to be a small bid immediately follwed by a matching ask, or vice-versa.
There is at least one ping-pong per minute, perhaps more. The average values of X and Y creep up by 1-2 USD every few minutes. Sometimes X stops before hitting a substantial wall, while Y keeps creeping up.
The effect is to make the mean price move up steadily for many minutes. Presumably this convinces other traders to revise their orders upward, so the ping-pong can continue creeping up as the nearest sell barriers move out of the way.
This ping-pong has been going on between dumps since dec/30 at least, with some interruptions.




