Quote from: timmo11 on June 07, 2011, 02:08:04 AM

How come it is fairer than the arithmetic mean?

Quote from: TiagoTiago on June 07, 2011, 10:12:08 PM

I would like to learn the pros and cons of each as well

The geometric mean is the "correct" mean for ratios, which prices are. It's the arithmetic mean on the log-scale:

Which chart looks more "correct"?

jerfelix is right of course: As a seller you're interested in the best "bid", and as a buyer you're interested in the best "ask". bitcoincharts.com has a calculator for larger orders, on the Market Depth page.