Random requests - some etiquette please

I've tried different ways to let other forum viewers that my friend list is full, whether as my location or in my signature, and the only thing I ever find myself bothered by is the fact I can't accept all of them. To me, they took the time to type my username, and I appreciate their interest tremendously. Every blue moon, someone will actually PM me first, or just after, and I believe that I have made a spot for every single person who has PM'd me with a request (please do not PM me. I'm am at the max), but it is getting increasingly difficult to find a friend who is inactive (or any of the other 93 things I unfriend for) to make a new spot.

I've deleted every random request that I haven't recognized from here.