One of my hangups as a GM is that I don't like allowing material (spells, equipment, etc) from books that I don't own. I have players who occasionally want to bring in things from Sourcebook X, and if I don't own it, my inclination is to say no.
Some RPGs just spit out book after book of gear and guns. (Shadowrun being a particular offender) As a GM, I am just not interested in piles of equipment. By the end of 3.5's run, and by the end of my patience with 3.5, I felt awash in an endless sea of extraneous bullshit.
...here's the other thing. I've had players offer to pirate, buy, or loan me the sourcebooks that contain whatever feat or toy they want to use. I already have enough shit I need to read without extra stuff being stacked on it. I also don't like the feeling of obligation this creates in me, as some stuff just isn't suitable for my game.
So I ask you this, fellow GMs: am I overly controlling with regards to allowing supplemental material in my games? I do admit that I have a desire to keep a tight control on the gear, spells, classes, races, skills, or whatever else goes into my game, even if that material is "official" and offered by the original party that published the game.
Disclaimer: You guys telling me that I'm a control freak probably won't change anything. I just want to see if I'm alone in my control freakishness, or if I have control freak brothers-in-restricted-arms out there in Blogaria.