It's not a scam, but it's not clear what it is.
The coins are behaving like a genuine new commodity with some amazing properties.
It's excellent for moving money between countries. It's stunningly good for microtransactions. It's very difficult to control companies which accept it. Those three properties alone give it a real value.
As a transactional currency, you could calculate a fundamental value as the volume of bitcoins in flux over a 45 minute interval. I.e., if I want to spend $10 on an e-book on the other side of the world, it takes 15 minutes for me to buy the coins, 15 minutes to transfer the coins and 15 minutes for the recipient to sell the coins. Those $10 are in the system and staying in the system for that period of time.
For microtransactions, you can buy objects or be paid for objects in tiny fractions of currency. This means you can charge for reading articles or watching programs without all the money going to the credit card companies or having to pay for a monthly subscription. Nothing else does this and it increases the volume of transactions, or currency in the system.
It can't be interfered with easily, so accounts which could normally be frozen could be stashed in Bitcoins and still retrieved anywhere in the world.
That stuff alone gives the coins *real* value. How much of hte $1000 valuation is "real" is unknown, but the rise from $0 to $1 is far more interesting than the rise from $1 to $1000. The fact that somebody might have owned it once at $1 doesn't matter. The coins aren't real and it's not clear what exactly is driving the market for them.