More context. (First off it is 5 years and one major layoff in between F:NV and today. Not all that surprising honestly)
Executive Producers
Larry Liberty
F:NV was his only game at Obsidian. (Seems to have worked on Aliens previously). Went to make his own game company. Failed.
Producers
Jason Fader
Cool dude, but again only worked on F:NV. He was laid off when Bethesda decided not to make a contract for his game Backspace. Also formed his own company, midly more successful.
Tess Treadwell
AGAIN F:NV was the only game (Well, a bit of very early production on South Park). Left on her own accord IIRC to pursue a job offering.
Lead Artist
Joe Sanabrina
I don't have to repeat every time right?
Went freelance. Doesn't really do games full time anymore.
UI Artist
Jason Sereno
Actually worked as the sole UI artist on more than one game. That being Alpha Protocol, Dungeon Siege III and F:NV (And again very early South Park). YMMV on how you interpret this. Was a more defining part of Obsidians history though.
Charachter Artist
Kevin Manning is also a cool dude. But as Sereno same 3-4 period and YMMV on his work.
Now
Aaron Brown
That was a big loss. Black Isle Vet and all that jazz.
Audio Director
Scott Lawlor
Captured by a Blizzard (As in better job oppurtinity even if he isn't director anymore)
Certainly Key Personel, but people probably remember Obsidians first Audio Director, Alexander Brandon, most fondly. Not really hard considering Alexander was probably one of the *big names* Obsidian had during.
...
Now I'm getting tired.
Well, theres the bigger losses following. Though in regards to writers as mentioned its not like Gonzalez and Stout have profiled themselves outside of Obsidian.
Other than that. Well, Frank Kowalkowski is obviously a big loss. Though, was snatched up by a Blizzard as well. Others left for various reasons.
On the topic of losses btw. only very few people left since the big layoffs in 2012 because of layoffs. For nearly every one of them it was a personal reason (location, job opportunities and so on)
5/5 programmers
They did hire Tim Cain and 3-4 other BI vets (bigger names as well) since then.
A lot of the others also have F:NV as their only Obsidian credit.
Chris was counted twice.
You forgot the Lead Animator (Left due to location)