GOD is infinite (according to Douglas Hofstadter).
If I were setting the rules (which I’m not since I didn’t write the OP), I’d say that multi-leveled acronyms should not be expanded more than one level. This restriction would eliminate the infinite answer that recursive acronyms get.
As for OK: either it expands to ‘oll korrect’ or else it’s not an acronym. Otherwise we could do Sn = tin for 1.5.
I seem to recall hearing that “L. A.”, if that counts, is the highest compression abbreviation, since the full name of the city is a rather long Spanish phrase which I don’t recall (the translation is something like “The City of the Angels of the God We Believe In and All the Saints in Heaven”)
Wait, Google to the rescue. According to this page, the name is “El Pueblo de Nuestra Senora la Reina de los Angeles de Porciuncula” (which I render as "Town of Our Lady the Queen of the Angels of -something-), which would give it a score of 27.5 (spaces don’t count, do they?).
So, can anyone beat that? <EG> (4)
Oh, and BTW (2.6), if we use dtilque’s single-expansion rule, then GOD is only 4 (or 4.3; I don’t recall the exact spelling), and GNU is only 3.6. I must admit, though, that php’s single-expansion score of 8 is still pretty respectable.
For comparison, DNA (deoxyribonucleic acid), which seems like it should be fairly high, is only 6.6.
What’s INTERCAL?
ITU-T is the International Telecommunication Union Telecommunication Standardization Sector, which is 73/4 = 18.25, assuming you don’t count the hyphen (source: Acronym Finder).
INTERCAL=Compiler Language with No Pronounceable Acronym, with 42 characters, giving a lowly 5.25
Using a related measure, www=0.33 which I think would be the absolute minimum. Of course it’s 4 in the standard measure.
Is w[sup]5[/sup]=“Which was what was wanted” 21, 10.5, or somewhere inbetween?
Can we have non-standard partial-acronym varitaions on IANAL, such as IANAFloccinaucinihilipilificator (~1.1)?
PS: HIBISCUS - Height Investigations to Broaden Information both on mean Sea level Changes and Understanding of Surface vertical movements in the Caribbean and adjacent regions (17.5) http://www.gfz-potsdam.de/pb4/ilp95/acronym.htm
Ok, OPer chiming in. Thanks for all the creative replies. Yes, the OP (5.5) was rather vague, here is a completely arbitrary set of ground rules. The acronym score is the number of letters in the expanded acronym words divided by the number of letters in the acronym. Thus, MIT does not count the two letters in “of” since it is not MIoT. This is to prevent dubious padding of the score with acronyms such as MTMC and LA. :dubious:
Please double check your scores before you post.
For lack of any standard authority, let Google be the final arbiter. An acronym is valid if you can google “op acronym” and see the acronym spelled out in any of the first 10 hits. (Note, this will disqualify some popular acronyms such as OP, but hey, ya can’t make an omelette without breakin’ some eggs)
Thus, C and HIBISCUS don’t pass. This seems to conveniently solve our other problems with recursive expansions, since “GNU’s Not Unix Not Unix Not Unix” isn’t on the google list.
Note: Google says AGA is many things, but not American Gastoenterological Association. Sorry. Google also gives a ruling on “ok”.
I think the lowest so far is OIC (2) and the highest so far is AI (11). Congrats to Achenar ! 
SNAFU (situation normal, all fcked up) = 5.2
FUBAR (fcked up beyond all recognition) = 5.6
TARFU (things are really f*cked up) = 4.6
BOHICA (bend over, here it comes again) = 4
MWR (morale, welfare and recreation) = 8.666666_
C3 (command, control and communications) = 15.5
Shouldn’t this be, “GNU’s Not Unix’s Not Unix’s Not Unix”? 
i18n for internationalization = 5.0. Not a record-breaker and not playing by the rules, but I always thought it was clever shorthand.
I got close, the ABAA (Antiquarian Booksellers’ Association of America) at 10.25.
Well, in this case, INTERCAL is 0.
So is methylenedioxy-n-methylamphetamine
8 with MDMA or 32 with E?
The E stands for Ecstasy, does it not?
Actually 10 even. You can’t count the of. (note the rules that have recently been posted.)
I was kinda kidding, with E. Just thought it was slightly tweaking the rules.
As recompense I’ll offer up CCITT (Comité Consultatif International Téléphonique et Télégraphique) at 11 even.
After doing a little research on this, it seems that most stall around 10.
Whoops! Googling to check my answer I found:
ITU (International Telecommunication Union) at 11.66.
Why does the ‘preview’ have to so close to the ‘submit’.
iff = “if and only if” Does this score 1.33 ?