Users are expert in knowing what they need to accomplish, but not in knowing how software ought to be designed to support their needs. Allowing users to design software through feature requests is the worst form of disaster by committee.
Wise words by Stephen Few from Information Dashboard Design (2nd edition). I substituted ‘users’ instead of ‘customers’ to underscore that to properly design for users, their needs must first be uncovered through various research methods (e.g. contextual inquiry) rather than by asking the user “What do you need?”