Since New Liberty Standard is currently the only 'open' exchange service for BTC to USD. Then it goes without saying that their is no 'real market' to help calculate a market price or other market influences from...
'Which came first ? The chicken or the egg ?' Well, in terms of evolution the chicken of course !
However, I understand what you mean and other 'closed' BTC to 'whatever' transactions will of taken place, probably. This is one issue concerning the usage of a sudo-anonymous currency and then trying to calculate market influences from transaction that don't exist ! You have to start somewhere.
"You can easily create a ฿/$ exchange service. Just provide a place where anyone is able to post bid/ask prices. Whenever there are corresponding bid and ask a deal would take place. A classical market."
I agree and such a service already exists for eCurrencies http://exchangezone.com/
- Now they just need to add Bitcoins
I'm already trying to build an exchange calculator and exchange rate predictor using a Neural Network and 'known' factors.
I will be using Liberty Reserve for my exchange service and they accept USD, EUR and 'back' payments by Gold.
So, my Neural Network model includes; XAU (Gold), EUR, USD exchange rates, the New Liberty Standard and Total Daily Block generation Rate / The Finite Number of bitcoins... and more.
Oanda Historical Exchange Rates - http://www.oanda.com/currency/historical-rates
Of course the value of Bitcoins has 'nothing' to do with the EURUSD at the moment, but these types of models are certainly useful in the future and can go along way to making our exchange rates behave like 'real' markets.