I agree with you there, abbreviations are most probably the product of the internet or at the very least, quick text transfer. I think that the fact that english is the most effected language (as far as i know) is in itself, proof of this, as from the very beginning it was the most commonly used language for communication on the internet. In hungarian, my mother tongue, abbrevations are ony starting to become common. Note that Hungary is in eastern europe and was, until 1989 dependent of the Soviet Union in every aspect. That means no Internet, among other things.
As for pronunciaton: I beleive it veries from country to country (or maybe even smaller territories). For example, I usually pronounce GOG the same way as dog, but with a g to refer to the starting post, and I beleive this is because Hungarian is such a language: we pronoince everything as it is written. Somewhat like japanese people pronounce romanji. It also feels okay to pronounce GOG because it follows my language's proper sound order: high-low-high. In other countries, this probably changes.
It also matters wether the individual pronouncing it knows if it is an abbreviation, or is proficent to some extent on the languege the original words come from. And last but not least, it matters who you are speakign to: If it's someone who knows about GoG, saying ghee-oh-ghee probably wouldn't surprise them, but depending on the native language and the language expertise of the two sides, ghee-oh-ghee might sound wierd if the other doesn't know about this paricualr abbreviation.
Okay, I wrote too much.
To answer the original question, I pronounce it like the word "dog", but with a g. It actually took me a second to realise what the two guys in hoods are saying when they go "ghee-oh-ghee".

Same here, we say "v v v .gog.com"

NASA was founded in 58, NATO was in 49 and ARPANET was in 62 (at least thats when it started development)

Holy crap. I'm amazed this topic has so much conversation.

I am down with gawg, dawg, but I often wonder if we should be a bit more upscale about this.
http://www.washingtonpost.com/wp-dyn/content/article/2006/06/20/AR2006062001271.html

Wow, we sure got sidetracked here. Anyway, I'll indulge in your curiosity, hope this will prove helpful to you.
http://en.wikipedia.org/wiki/English_phonemes#Consonants
the /g/ is a velar consonant; in the back of the mouth. Surely you have seen this chart in your introductory course? Look up the i and the o while you're at it:
http://en.wikipedia.org/wiki/English_phonemes#Vowels

of course, of course. If you decide to go with a certain pronounciation, it'll change more into a word and less into an actual abbreviation. My point wasn't that pronouncing it `gee-ooh-gee' was wrong, impossible or weird. My point was that what is more `effort' is a lot more complicated than how far you have to open your mouth. People strive to reduce effort in all relevant dimensions, though the order in which they are prioritized differs vastly per language, and interspeaker differences in the realization of phonemes also makes these restrictions have different effects between speakers. This is basic optimality theory, of which you probably also have seen a bit in your introductory course (it should at least have been mentioned).

http://en.wikipedia.org/wiki/List_of_classical_abbreviations
there you go.

of course A LOT of modern abbreviations emerge on the internet these days. The medium is perfect for them. However, that says nothing about abbreviations in general, or how they are pronounced. The fact that these days a lot of new abbreviations emerge (and thus there will be more of those abbreviations pronounced like the word they spell) might give the impression that it is an internet phenomenon, just because most of the abbreviations you know that are pronounced this way stem from the internet era. But you're making some pretty basic statistical mistakes there :) There have been mentioned several counterexamples from the pre-internet era already.

I need to respond to this, because it wasn't my intention at all that you'd interpret it like this. I assumed that your statement was meant as a joke, a whimsical remark to underline the fact that in the end it all comes down to personal preferences. I decided to go along with it and complete the joke by replying with the contrasting sentence. No mockery was intended :)
Please do look into it! Phonetics, phonology and linguistics in general are very fascinating subjects. Check out works by Steven Pinker for some very accessible introductions (I might not agree with a lot of his views, but they do succeed in showing how fascinating language can be).
EDIT: Pinker's books are more about Linguistics in general, by the way, not phonetics or phonology in specific.

See 5:05 at the following link:

http://www.youtube.com/watch?v=Ad0de_JHJJQ&feature=related

Nog but with a G.

Well since unfortunately most of my friends dont like old games, I dont have to say it aloud too often, but in my langue I simply say each letter G.O.G.

I asked about the letter "g", not the phoneme. The "g" phoneme isn't used to pronounce the letter "g" when said independently of a word.

/ˈdʒiː/; is how Wikipedia transcribes "g" in IPA. I hope we can agree on that pronounciation.

I absolutely agree that the "g" phoneme, or the "g" sound to those not familiar with phonetics terminology, is pronounced at the back of the mouth while speaking English.

No, you must have misread, or have a completely different idea on how the pronounce `gog' (which would explain a lot of our disagreements :D ). /ˈdʒiː/ is the j in jeep, as the helpful list under the chart shows you (and the `g' in gin). /g/ is the g in gut or game, and the g I use when pronouncing GOG.

Exactly. /ˈdʒiː/; is the j in jeep and the g in gin - and the sound of the letter g, as pronounced outside of a word.
We're talking about the pronounciation of each letter seperately here, remember?
We're not talking about "gog" that rhymes with "dog".

Oh, haha, yes, you're right. I got confused there. Sorry about that.
Anyway, why did you mention the position of the /ˈdʒiː/ in the first place? I never said anything about it being in the back of the mouth before you mentioned it (and I got confused as to about which `g' we where talking >_> ). I only was talking about the vowels..

I pronounce it like the word "goggles". So "gawg".