So it's a run on Gox then ...
A 20%+ risk premium over the other main USD exchanges would certainly point in that direction.
MtGox 24h Volume: 46280 BTC
Bitstamp 24h Volume: 11791 BTC
Makes no sense, you don't cash out of Mt. Gox by buying bitcoin rather than by waiting a month for a USD wire.
Do the math, if you're a whale with that much buying power you have let's say at least 100k USD on gox.
So if you'd like to "cash out", you'd have to buy @ ~$115 (let's make it easy and ignore the slope). So you get 100.000/115 = 869.57 - 2.61 (0.3% Fee) = 866.95 BTC.
Now you transfer them to an other exchange (Bitstamp) to cash out to USD (again we ignore the slope which is even higher @ bitstamp), so:
866.95 * 99.98 = 86677.66 - 260.033 (0.3% Fee) = $86417.63
So you just lost $13582.37 because you didn't want to wait a month.
/dit: Looking on the volumes of the recent rally and the fact that there was a single 1500 BTC buy order taking down the $115 wall, I think it's safe to take those numbers * 10.
I suspect people are more concerned about getting their money out at all, than just waiting a month. Why else would you pay a 20% premium?
If you were buying coins now, you wouldn't be wiring funds to Gox and paying a 20% premium. The only people who would pay that are those who (unfortunately) have fiat funds there waiting already.