Which of the above questions is more important for testers to ask?

Let’s say you are an is-there-a-problem-here tester: 

• This calculator app works flawlessly as far as I can tell.  We’ve tested everything we can think of that might not work and everything we can think of that might work.  There appear to be no bugs.  Is there a problem here?  No.
• This mileage tracker app crashes under a load of 1000 users.  Is there a problem here?  Yes.

But might the is-there-a-problem-here question get us into trouble sometimes?

• This calculator app works flawlessly…but we actually needed a contact list app.
• This mileage tracker app crashes under a load of 1000 users but only 1 user will use it.

Or perhaps the is-there-a-problem-here question only fails us when we use too narrow an interpretation:

• Not meeting our needs, is a problem.  Is there a problem here?  Yes.  We developed the wrong product, a big problem.
• A product that crashes under a load of 1000 users may actually not be a problem if we only need to support 1 user.  Is there a problem here?  No.

Both are excellent questions.  For me, the will-it-meet-our-needs question is easier to apply and I have a slight bias towards it.  I’ll use them both for balance.

Note: The “Will it meet our needs?” question came to me from a nice Pete Walen article.  The “Is there a problem here?” came to me via Michael Bolton.