In non-enterprise sales often there is no prospect before someone becomes a customer – i.e. they just sign up. In fact, I'd go so far as to say that's the case

In non-enterprise sales often there is no prospect before someone becomes a customer – i.e. they just sign up. In fact, I'd go so far as to say that's the case in most web startups. As such there's often an (ideally small) segment of paying customers that are outside of the market you can service well with your offering and if they become pushy (i.e. begin making requests / demands that pull you away from your target market) it would be better if they were not a customer than for the company to lose focus trying to make them happy.