Oftentimes it seems there's more risk in saying "yes" than "no" to a client's concern or inquiry. For that matter, anyone who comes to you asking for a fix or solution is easier met with a negative than an affirmative response. That's because with "yes" comes additional time and effort on your part. But what if you changed your mindset? What if the risk were actually in saying no?
Ultimately, there's a lot less work for the employee who says no (think compliance departments). If you say yes, you may have to do more work and then take a risk for doing that work. And frankly, it seems that some service people don't see the benefit of saying yes. It's too much work. But eventually, much less work may lead to no work (especially if you're in an industry providing services to clients).