"DFC" is a relatively new term, actually, and there is one unknown taper somewhere that said he was "dead f*cking center" and used that acronym on a source and it then spread like wild fire. I think I first started seeing it on sources around 2002 or so, but it could have been 2001, but not much before that.
Back in the '80s and '90s, the tapers I ran with at that time used the same conventions that theater ticket sections showed on their charts and tickets, "CTR" (center) "LOC" (left of center) "ROC" (right of center).
(FOB) meant anywhere in front of the SBD area, and since the bulk of open taping done back then was in large venues for DMB, GD, Phish, and WSP, it's meaning was fairly straight forward and everyone knew it was not the same distance from the PA as the taping section, (TS, or OTS for "official" taping section), usually behind and occasionally next to, but never in front of the SBD.
Today, I think the meanings of FOB, DFC, and OTS are so much more relative, as Brian points out, and without actual location specifics, really does not indicate what actually was the physical location relative to the stage.
The below source info is what would tell any taper that knows the venue precisely where the recording was made:
http://bt.etree.org/details.php?id=516445
The Black Crowes
July 5, 2008
Charlottesville Pavilion
Charlottesville, Virginia
***16 bit***
source: B&K4022(ortf)>Sonosax>744t (24/48 )
location: fob/slight loc, Row 19, seat 11, stand at 7.5'
transfer744T>wavelab(fades/resample/bit depth)>cd wave>flac
recorded & seeded: craig davis
One Set
Disc One:
01 Intro/tuning
02 Movin' On Down The Line
03 Goodbye Daughters Of The Revolution
04 Hotel Illness
05 Thick N' Thin
06 Walk Believer Walk
07 Young Man Old Man
08 There's Gold In Them Hills
09 Boomer's Story*
10 Seeing Things
11 Welcome To The Goodtimes
Disc Two:
01 Quinn The Eskimo (The Mighty Quinn)
02 Wiser Time
03 Jam>
04 Thorn In My Pride
05 Wounded Bird
Encore:
06 She
07 The Night They Drove Old Dixie Down
Notes:
* a huge moth flew into Chris' hair during Boomer's Story
and he jokes about it