Never use “e.g.”
Perhaps because I suffered through several years of Latin in school, I know that e.g. stands for exempli gratia ("for example") and that i.e. stands for id est ("that is"). Most people, however, were lucky enough to avoid taking Latin so they never had to memorize passages from the Aeneid and poetry by Horace. (I've long forgotten almost all of the Latin grammar than I once knew, but I can still recite the passages that we had to memorize.)
They also often don't know what "e.g." and "i.e." stand for, and this can sometimes lead to confusion, particularly when it comes to interpreting standards.
In more than one case I've seen "e.g." incorrectly interpreted as meaning "that is." When this happens, something like "must use strong encryption (e.g. three-key 3DES)" gets interpreted as meaning that three-key 3DES must be used. And the people who do this misinterpretation often don't believe any of the many sources that you can find on the Internet that try to clarify this.
So now if I ever see the abbreviations "i.e." or "e.g." in a draft of a standard, I always recommend that the abbreviations be replaced with "that is" or "for example" respectively. I haven't found anyone who will argue with the meanings of things written that way. At least I haven't found them yet.