[gregjor]

Some clients do understand estimates and the nature of software development. A tech firm or a software outsourcing firm, for example, will have more experience and understanding. Other customers not in the software business probably won't understand that, and they expect binding estimates because that's what they get from their other vendors. I tend to work with companies that make money, depend on technology, but aren't in the tech/software sector. A trucking company or a law office, a medical school, for example. Their idea of how binding an estimate is will differ from how a web marketing agency interprets an estimate.

Sure, don't do that. And yes, stay in constant communication with the customer. If you can estimate at all then you can break the tasks down to make the estimates even more realistic and achievable.