When shouldn't you contribute to an RRSP?

As RRSP season quickly approaches we are going to hear more and more about the benefits of contributing to an RSP, and how little Canadians are actually investing. As important as it is to start saving for retirement as soon as possible in one's working career, it is also advantageous to know when you should NOT make a contribution to your RSP. Here is a good article explaining when it just doesn't make good financial sense to contribute: When Should You Not Buy An RRSP?