Why is this a good interview question?  Because it reveals a tremendous amount of insight into the candidate.  While typical questions solicit standard responses from candidates, this question allows the interviewer to look into the character of the candidate.  In responding to this question, the candidate will be more inclined to reveal a little (or a lot) of his or her true nature:

• Are they an optimist or a pessimist?
• Do they believe that hard work and some degree of luck have gotten them to where they are now?
• Do they reveal some sense of entitlement?
• Or worse yet, do they believe that a series of mishaps and "bad luck" have landed them in front of you, interviewing for this job they don't want?

So, ask yourself, ask your job candidates and ask your employees, "Are you lucky?"