Bitcoins only have value due to their function as a wealth transfer mechanism. If you look at the wealth being transferred, you can derive a theoretical minimum price for bitcoins based on the fact that there is a minimum 1 hour transfer period. If a person buy bitcoins for $x, transfers, and then the receiver immediately sells for $x, there is that 1 hour transfer period where there's more demand for bitcoins than supply. So, what is the minimum value of x?
According to bitcoinwatch, 17,738.09 bitcoins were sent per hour on average. At a price of $8.30924, that means $147,390.0469516/hr was transferred on average. If there is a 1 hour transfer period and no one holds bitcoins for any additional time ever, then that is the value of the entire bitcoin economy. Since there are 6,993,100 bitcoins, that translates to $0.021/bitcoin.
Of course, a few weeks ago it was $0.094/bitcoin - there were more bitcoins transferred per hour (45,744.18) and the price was higher ($14.02).
This doesn't take into account transfers made outside of the bitcoin protocol.