Debts denominated in bitcoins I was reading an ebook, called Bitcoins: what they are and how to use them, the book says


  ... it would be a fools bet to take a promise to pay a debt in
  Bitcoins, as they will by definition, become increasingly difficult to
  obtain.


This doesn't make sense to me; just because the number of new Bitcoins being produced will decrease, that doesn't mean they will be harder to obtain, because people can still buy and sell existing bitcoin. The quoted text seem to imply that the value of bitcoin will always go up, or am I missing something?
That is indeed what that author is implying, though I think his conclusion is wrong. Any good currency will increase in value over time, or ideally the money supply will increase at the same rate wealth is added to society, which would imply its value remains constant. 

This is distinctly different for instance then the USD which is intentionally being rapidly inflated by the Federal Reserves quantitate easing policy. 

Bitcoin does not match the rate of wealth creation, and coins become more difficult over time to acquire, but the same is true of gold and people have been paying debts in gold for centuries. Perhaps its a good thing to be a little foolish.