Another omg version like omgooses and others, it's used now and then on forums and chatboxes.
People probably added google cuz of google's popularity.
I just had hot sex with Gabe Newell!
omgoogle that's hot!1!!
An expression of exasperation when someone should have heard of something already based on its wild popularity. Having this phrase used on you implies that you should use an internet search engine to look it up to save yourself from further embarrassment.
I have a question. - person 1
NO YOU CAN'T HAS CHEEZBURGER! - person 2
What? No, why would I want a cheeseburger, that makes no sense? - person 1
Omgoogle... - person 2
Oh...guess I should google it. - person 2