@datafish, what kind of product or service would that be? Is it truly unique? I think I've seen everything you can possibly call a product or service, and nothing is unique in the sense that all of them are merely variations of something else.
I don't have anything specific in mind; I was just thinking out loud. What if you used BTC to buy early shares in Mastercoin or Ethereum? There is no clear valuation in a virtual startup on the first day of issuance, is there? Would you pay capital gains sometime later, once the startup becomes successful and you use the proceeds to buy some conventional product or service?
Yes, I mentioned alt-coins. Those things don't have fiat value yet, but like Peter says, most will consider the fiat value of the bitcoin value as the value of the alt-coin.
So, now there are a ton of alt-coins, and in an attempt to peg a value to them, some are accepting IPOs for pre-mined coins. The fiat value of those coins will therefore be equivalent to the bitcoin value converted to fiat at the time of the transactions.
The value of the coins later goes up or down on it's own, depending on the supply and demand once people start using those coins, trading them, exchanging them, etc. Most are still pegged to the bitcoin. Very few are pegged to any other value.
At least one is trying to disassociate it's own value separate from bitcoin, but using it's own value. Basically the bitcoin value will follow that coin's fiat value, not the other way around.
Only time will tell. All of these coins are much too young to really have any value (but still, people are sending BTC / fiat.)