> "that's no problem, we estimate it will take an additional X hours or dollars to implement that. Would you like us to update the proposal? What happens in pr

> "that's no problem, we estimate it will take an additional X hours or dollars to implement that. Would you like us to update the proposal? What happens in practice is they didn't realize they were asking for additional features -- they thought they were asking for D, E, F (etc) all along in the initial request. They just assumed "Email signup link" also meant spam handling, re-sending, prevention of double sending, etc. Good product managers account for these obvious things, and leave padding for the unexpected. But good product managers are rare. Most software developers I know have never even met one. So instead you have a political dance where you try to plan for the things they aren't telling you, along with all the _expected unexpected's_ that come up in normal software development, and set your deadline's appropriately. Definitely the worst part of software development.