Bitcoin Q&A: The Rules of Bitcoin (part 2)

This is the second part of the answer to the question: "What are the rules within Bitcoin?" How does robust consensus and decentralized decision-making affect the predictability of the system? How does this compare to certainty and predictability within traditional financial institutions, such as interest rate changes? I can't predict what the U.S. interest rates will be next year, but I can predict what the rate of distribution (block reward) of bitcoin will be in 100 years.