If Hive drops too much, HBD would stop being generated thus commencing deflation through eventual HBD burns and direct conversions.
HBD can fluctuate a little, but general tendency is to always go back to USD parity. So, it's always good to buy HBD every time it's value goes below 0.99 USD and always sell when it's above 1.01 USD
RE: HBD is NOT at risk! Understand why the price of HIVE currently does not affect HBD