Here is a blog by Chris avellone.
Read the dead money section.
This part goes well with what Ulysses seems to be doing
So why did we choose survival? Well, the question of Survival sums up questions I've had about Fallout as its timeline advances... the post-wasteland's gotten more civilized as the decades since the nuclear war have gone on, and when I was scripting Dead Money's layout, one thing that kept coming up was that I missed the desperate "Road Warrior" feeling when I hit the wastes. I miss being in a situation where I'm scrounging for every last bullet, water's precious, and I have to fight tooth and nail for any edge I can get. That goes double for the environment, I want it to be terrifying and be something you're constantly fighting against, Vault 34-style. I confess, there's been times I wish someone would drop more nuclear warheads on the Fallout world if only to bring parts of it back to its roots, so I wanted to create an area in the Wasteland that felt just as desperate as you'd expect a post-holocaust environment to be.
The enclave I approve of the above post.
http://forums.obsidian.net/index.php?automodule=blog&blogid=1&
Something tells me NCR and legion wont exist outside of the Mojave after this. Their civilisation came crashing down.