I don't get how there can be "good" or "bad" customers?
I won't get into too much details here, but it's not that easy as you might think. Customers are just also people, and all people have their goals, habits and traits. This is why you have a target audience, because you could never ever satisfy all your potential customers who arrive at your site. The difference between "good" or "bad" is for example that there are also customers who will always complain, never really say what they want, or want to dump prices all day long. I get your point about the feeling that also matters, but people in my audience do know that for example problems with legacy code can be a serious problem. Other people might not of course, but then it is not my target audience. I am only looking for customers who are really interested in their own products and want me to help them or build them, you know?