When you don't believe in God???

Actually, it doesn't bother me. It used to bother my parents, specifically, my dad... and he isn't even religious!
In my personal opinion (which is all we have here)saying, "Oh my God!" isn't using his name in vain. In vain means without respect or seriousness and I just don't see it as a lack of respect. Also, I'm always using it when I'm being MOST serious.

Besides, there are many different Gods by many different names just as there are religions. God is actually a 'generic' term used i.e. Christians say Lord or my Lord and let's not forget Jehova, Yahweh Buddah, Allah, etc. Let me not be sexsist because there are many Goddesses too including Isis, Athena, Aphrodite... just to name a few.
I think Shakespeare said it best with, "What's in a name? That which we call a rose by any other name would smell as sweet."

Thanks for sharing anyway! You've earned your positive mark= )