Any of the big Bitcoin businesses would be interested in stability, including of course MtGox.
Why now? Gox has been taking $ hand over fist during these last few days and I didn't see any mystery walls then.
There's also a number of people who have 50k-300k coins who probably have cashed out 1-5M. If I owned that many coins, I'd keep a nice chunk of cash on MtGox to prop up Bitcoin as needed.
If I owned that many coins I would use them to manipulate the market and turn them into more coins while BTC is still in the triple and (possibly) double digits. This is the time for the whales to turn huge profits into really huge profits. Once BTC hits the thousands it will not be so easy. That's when the market really needs propping up.
The interesting thing is, the coin dumps have stopped. No one has sold a huge chunk of coins. No one wants to cash out anymore? More evidence the coin dumps are to move the market down, not to take profit.
Or they're simply waiting for the price to go up to take bigger profits. Look, we're going to test 120. Let's see what happens...