As this article points out, you have to be the bad guy and Just Say No most of the time. However, when a large subset of your users request a certain feature, the best response is often to refactor your design. Don't just add the feature. Figure out why they're requesting it. In other words, figure out why the current design is lacking. At that point you can come up with a new design which lets your users accomplish what they're trying to do.
User interfaces age like code bases in this way. If you keep adding to them, they get really ugly really quickly. If you instead take the time to refactor them, they can remain beautiful while becoming more capable.