First off, "fiat" means "by government decree". Without that government decree, something cannot be fiat. Get over it, y'all.
Nothing has intrinsic value. Value is a property that is bestowed upon something by a living organism, whether it be tangible or not. A squirrel can value a nut, but that nut has no value without the squirrel. A person can value a video game they download off Steam, despite it having no tangibility. A rock can't value anything, but a mason can value a rock.
I don't really like the argument that an asteroid full of gold could hit us and cause the gold price to plummet. That's far too unlikely to take seriously. What I think is a much more relevant argument is that an asteroid full of gold that doesn't hit us has no value because it is of no use to anybody. Gold does not have intrinsic value because its value is completely dependent on people being able to make use of it. Some people might want it because it looks pretty to them. Others might not like the look of gold at all. For most people on this forum, gold's value comes from its increasing value relative to the dollar. It's circular. Gold's value comes from it's expected value in the future. Most of y'all who claim that gold has intrinsic value will just leave it in a drawer or somewhere equivalent. I doubt anybody here owns an electronics factory. Maybe there are some dentists. I'm sure there's a small minority that actually has some use for gold, but for the majority it is just a chunk of metal that will sit there and do nothing. Y'all just assume that other people will be willing to trade more dollars for it in the future. Or Euros, I guess. You're certainly not going to be able to buy gasoline or order something off the internet with it. That's because gold sucks as a currency in the modern world. It worked great for a long long time, but so did the horse and buggy.
A large part of Bitcoin's value also comes from the expectation of a greater value in the future, but in addition to that, Bitcoin offers greater utility than gold to most people. I've never heard anybody explain the utility of a few gold coins sitting in a drawer. The only worthwhile thing you can do with gold coins is sell them for a currency that can actually be traded for things that you do have use for. That's a pain in the ass. And that person that buys them from you probably wants to copy down your driver's license information so they can come get you if its fake. Because it is easy to fake a gold coin. It is not easy to fake a bitcoin. After the initial setup at MtGox, it is extremely easy to buy and sell bitcoins. Easier than buying gold or silver. No shipping charge. And look,
you can buy an iPad with bitcoins. Can you do that with gold?
Value is completely subjective. Dollars do have value. Real value. Because you can trade them for damn near anything. It just sucks that it takes more and more dollars to get those things. It also sucks that it is expensive and slow to send dollars around the world (although still cheaper and faster than gold). The only advantage gold has over dollars is a relatively guaranteed scarcity. Gold's portability and transferabilty sucks, though. It is very clunky to use as a currency in the modern world. Gold had a good run, but times have changed.
Would somebody care to explain how they believe that value can be an intrinsic property? Good electrical conductivity is an intrinsic property of gold. So is good malleability and corrosion resistance. Gold has these properties even if it is in another galaxy. That's what makes those properties intrinsic. Gold only has value on Earth, though. That makes its value subjective. Just like Bitcoin. Gold will make a better necklace, but Bitcoin will make a better currency.