Maybe it's just me, but "no" isn't as much of an option as it seems from the outside looking in. I've had much better results by refining and redirecting outside requests than by just denying them outright. There's also the chance that whoever you just denied will now just try to find a way to get what they want without you.

If you're in a place where you are constantly being asked for unacceptable things, there's a chance that one of the parties in those exchanges is going to be asked to leave. If we accept that premise, then the likelihood of you being dismissed goes up as you deny more requests from more people.

I use "no" rather judiciously and I avoid saying it in front of too many people at once. This isn't about cynically appearing reasonable as much as it is about being polite.