With a deflationary currency, people have the tendency to hoard,
Even though the currency is still inflating at a little over 10% per year for the next year or so, there are people convinced that the future demand over these next years will cause the exchange rate to rise. So they are holding their coins ("hoarding", as you describe it), and the exchange rate is rising.
it is harder for businesses to make money in this kind of deflationary environment.
If these people weren't investing in bitcoins they would be putting their wealth in something else. But for now, they're taking this money they would have invested elsewhere and have put it in bitcoin and are not spending it on consumption. They wouldn't have spent that money anyways .. .they are speculators and investors, and they invest with some of their income and wealth and use some for consumption as well.
If I am not mistaken, since the inception of Bitcoin economy, in this system, very few business has been more profitable than hoarders.
Agreeing with you 100% on that. Yet nearly every day there's some type of Bitcoin-based venture launched.
So, if it's not good for trading, it's destined to be a tool for speculation?
Nope, because there still are reasons bitcoins are useful for spending. What is the easiest way to send money to your favorite online gambling service today? Bitcoin. Bitcoin is the largest online payments system that works without participation of the banks, and thus gaming services use it without concern about funds being frozen. How is BitcoinStore able to undercut Amazon and NewEgg? Because they use the lowest cost payment network (fees about a penny or less) with no chargeback risk -- from customers anywhere in the world. And on and on. There will be people using bitcoins for the benefits of bitcoin. Merchants will adopt bitcoin because there are bitcoins to be spent. It matters not that some value of bitcoins will not be used in spending. If you are concerned about that you are looking at the wrong side of the equation. Or at least one there is no control over. Bitcoin is not an academic study or theoretical concept. It exists today. If there will be huge amounts of value transferred into it, there will huge amounts of value transferred into it. That's the way free markets work.