The fact that ~ 6000+ bitcoins have already been listed at an ask price of $145, and fulfilled, should say something.
I am not surprised that 6k ask wall was filled, but rather someone actually placed an 6k ask.
I find it very risky to sell btc on mtgox.
Assuming the person(s) placing that ask wall don't:
(1) Have special relationship that allows them to withdraw for some additional fee.
(2) Have insider information of an upcoming partnership announcement that resolves all withdrawal issues.
They may still just be betting that the price will fall. They can then re-purchase those bitcoins on Mt Gox at a lower price.
Thus far, that hasn't been working out well for them.