With $20 - $30B daily trading volume, if the transaction is only for $12,400 BTC, people would have not feel panic.

With $31B daily trading volume, it is about 453,306 BTC equally and they have reasons to worry about price falls if all or most people who receive distributions from Mt.Gox will sell their bitcoins on the market.

Because 141,686 BTC is about 31% of daily trading volume, smaller or bigger depends on different day and its total trading volume.