Youre actually right. It jumped from around 15.50 to a bit above 20 in one day.

The point stands though, very short term, massive spikes.

You misremember.

On Jan 23-24, there is a 36 hour period where it jumped from $16.8 to $19.2. http://bitcoincharts.com/charts/mtgoxUSD#rg30zczsg2013-01-24... That's the closest scenario I can find. Certaintly not "$15.5 to $20+ in 12 hours".

On what day? Can you link to a graph showing this? I see a more steady progression from 13-15 to 21 over the last 30 days.