I'm trying to give this trait thing the benefit of the doubt, but having an on/off switch (that happens to waste a trait slot) for Fallout-style humour, in a Fallout game, just seems bizarre to me.
"Fallout humor" to me, is the dark and sarcastic wit of the first game, which will likely be present in New Vegas whether you use this trait or not. It's true that pop culture special encounters have been around since the first game, but in the original Fallout there were only a couple encounters that were minor nods that you had to go out of your way to stumble across by pumping points into Luck and Outdoorsman. In a sense New Vegas is a bit closer to Fallout 1 in that regard as the ability to stumble across pop culture encounters is controlled by how you build your character.
I think Fallout 2 handled the pop culture encounters extremely poorly by constantly shoving them down the player's throat regardless of their build, and there were instances where the game broke the fourth wall even in town. For example, asking the New Reno boxing ring midget if he's been in the circus leads to a rant about how you're a generic Fallout player character. That's not Fallout humor to me, the original Fallout never broke the fourth wall outside of special encounters and even then I don't remember characters actually acting like they were in a video game.