I wonder how easy it would be to manipulate the market of bitcoin. If a few people were selling between each other would they be able to inflate the price ? It's below $500 now, and it peaked at over $900 on mtgox a few hours ago.
As Bitcoin grows in market cap, volatility will reduce, quite considerably I think.
Eventually BTC might have a very low volatility and become to investors more like gold or silver.
The notional value of all bitcoin is/was $6 billion. The actual market is some smaller value that you would have to estimate from transaction volume.