if the coin using bancor is good, liquidity will be there on the exchanges. if the coin is bad, the reserves are going to be eaten up pretty fast as instead of selling into bad liquidity everyone will convert their holdings into the reserve.
The liquidity on the exchanges is not just a function of the utility of a coin, but also of its
scale. A local currency, for example, may incentivize local commerce and be useful as well as beneficial for its users, however, it might not have the scale required for achieving continuous liquidity in the current bid/ask matching model.
Using Bancor, the demand generated by the utility of a token would definitely be reflected in its price, but
not in its liquidity (or lack thereof). The removal of the critical mass barrier to liquidity is important not just for the long-tail of currencies, but also for the newly issued that are still in their early growth phases.
It is clear that both liquidity and price-discovery can be achieved for large-scale tokens using the existing solutions, which would be like saying that true talent would eventually be discovered and featured on TV. Still, YouTube not only reduce the barrier for a talent to be discovered, but also enables us to enjoy a significantly larger variety of talents.