One of my teachers had a story about his local BicycleRepairMan, who had a sign in his shop:
CouldYouJust .... costs 40 Kroner
(The sign was in Danish, so in fact it said Bare lige .... koster 40 kroner)
The point of the story is, naturally, the emphasis on getting the requirements sorted out, and getting the customer to realize the CostOfChanges?.
When someone asks you "CouldYouJust do this?", he is often thinking "I CouldDoThisMyself in no time."
If you suspect that this is so, the appropriate response is to ask him how. Who knows -- he may have
a good plan in mind, and you've saved face by not claiming it's impossible. If he has no plan in mind,
but is not completely clueless, then attempting to answer your question may help him realize why
you "couldn't just." True enlightenment must come from within.
But, this is also one of the great consulting questions. "Could you just store it in a file?" always results in either learning for the consultant or a dramatically simpler implementation for the client.
See also: JustIsaDangerousWord