The seller might not have known, but now you know, and you can't un-know the salvage history. Take fair market and deduct 30%, and know that if you ever go to sell it, even at a discounted price, the pool of buyers will be smaller.
As long as you know what you're buying with a car with salvage history you'll be fine, it's the people who buy it thinking they are the smartest guy in the world and then when they go to sell it have complete amnesia about the salvage hit to value.
Eyes wide open on this one.
My 993 has old salvage history, but I can't see the title when I'm driving!
---Adam