One thing I've noted before is that I like random tables a lot, especially in the middle of play. They add a bit of unexpectedness to one's experience as a GM, which is really nice because its probably my favorite part of being a player. It's one reason I don't like totally communal setting building in spite of what my laissez-faire attitude would suggest; it removes the sense of wonder and exploration that I love most about RPGs, D&D in particular. It particularly works against my favorite part of being a GM, which is world making.
As a result, I tend to keep a lot of setting stuff close to my chest so it can be revealed in game. My compensation has always been to be accommodating when it came to the player's decisions on what to play - even the oddest or seemingly off kilter sort of PC could be from another time or dimension or something. I realize that this is because I'm trying to show them the same courtesy I'm requesting of them. They are agreeing to let me run the setting I want (within reason), so it seems only fair they get to play what they want (also within reason).
In this sense, I've always thought of the setting as my PC when I'm GM-ing, being that its my way of interacting with the game itself. Obviously it doesn't line up exactly, but there are a great deal of parallels - The player's character can die, the GM's setting can be irrevocably changed by PC's actions. Random tables can be spells, attack rolls, or a background generator. Showing off the stuff marked on your map is not to far off from talking about a particular PC's back story or foibles. There are different styles that match up too - a player may be using a PC who can't die unless they say its kosher, or someone may run something where no one can beat Caine.
This seems even more obvious to me since I started playing in and running FLAILSNAILS games. My paladin can have his sunsword magically snatched away from him by a Jackal-Man of Cobalt reach, or Akenia's Flame Gigas can be totally blindsided by someone's Dungeon Crawl Classic spells. We are all playing the same game.