If you are not sure, get the person involved and see how it pans out. If the person requesting can be asked to "do some work" - diagrams, functional spec, mocku

If you are not sure, get the person involved and see how it pans out. If the person requesting can be asked to "do some work" - diagrams, functional spec, mockups, etc, then it shows commitment. Most cases the user might not be interested, so then it fizzles out. If he/she is really passionate about it, it may turn into a good idea since someone is actually giving it proper attention.