&gt;  Ripple sets the threshold high (80 percent) to provide adequate protection from double spending. But by doing so, it gives a submajority the ability to block transactions that they perceive to be repugnant.<p>So in the context of an exchange, a small minority could, say, stop short selling or halt the market in a high volatility environment.  All this ads liquidity risk which in turn reduces the value of the infrastructure.