Given the current economy and high unemployment rates, saying no to a job offer could seem counter-intuitive. There are, however, certain situations in which it is perfectly reasonable and sensible to turn down a position.
1) There is no room for promotion
The job might look good compared to other current offers, but just because the salary is higher now doesn’t guarantee that you’ll be earning more in years to come. The same goes for advancement. If another employer offers you more chance to make your way up the company ladder, it might be worth sacrificing luxuries in the present for the sake of the future opportunities. You do not want to be stuck in a dead end job with nothing to aim for; it can be extremely demotivating.