I used to do some proofreading work for a publisher* of magazines and books for teachers and childrens' librarians. It was an okay job (and of course, could be done in my pyjamas, which it often was), but I remember one pet peeve I had with the job very clearly. Several of the authors whose work I proofread didn't understand the difference between "i.e." and "e.g.," which always made me crazy. Even crazier than authors who didn't understand the difference between "its" and "it's."
I don't actually know what "i.e." and "e.g." stand for, although I think it's something in Latin. But I do know that "i.e." means, approximately, "that is..." while "e.g." means "for example." So it's very easy to work out which one you should use: i.e., you should try them out in a sentence (e.g., like I just did).
Those are messy examples but you take my meaning. So yesterday I was reading along in Candace Bushnell's (she of Sex and the City fame) new novel One Fifth Avenue, and I came to this paragraph:
"'Isn't that some kind of record for you?' Schiffer asked. 'I thought you never went more than four years without getting hitched.'
'I've learned a lot since my two divorces,' Philip said, 'i.e.: Do not get married again. What about you? Where's your second husband?'"
Now there's really nothing wrong with that. "That is, do not get married again." But I don't know. I think I might have used an e.g. there: "For example: do not get married again." It's debatable, I know. But once I had that in mind I couldn't get it out of my mind, and fifteen pages later, I was still thinking about it. So I ditched the whole book. (I wasn't really enjoying it all that much anyway.)
*Speaking of proofreading, I'm pretty sure publishers have just quit doing it. On the very first page of American Prince: A Memoir, by Tony Curtis: "All my life I had one dream, and that was tobe in the movies." Sigh.