I could rant about enormity (not the same thing as enormousness), which has been used a lot by reporters in the wake of the recent devastating, horrific, but not, strictly speaking, evil tsunami; or perhaps disinterested (not the same thing as uninterested), humorous (not the same as funny), or even momentarily (not the same thing as in a moment): but there are shorter, simpler expressions that get mangled all the time, and the fact that there are so many opportunities to get them wrong, when they are so easy to get right, leads to massively more irritation for a nitpicker who is having a bad day.
i.e. stands for id est, which is Latin for that is. It is used to suggest an alternative name or definition.
e.g. stands for exempli gratia, which by a rather less straightforward translation means for example. (Exempli is self-explanatory enough, but gratia means by/with/from a favor, and is sometimes translated as for the sake of.)
They are not the same thing.
If you refer to, for example, menswear (i.e. socks), you are saying, wrongly, that menswear means socks; that is, the Menswear Department is really the Sock Department. Which it isn't.