"It is a symbol of Irish art. The cracked lookingglass of a servant." -- James Joyce
I.e. versus e.g.
It is really annoying when someone confuses "i.e." with "e.g." If you are unsure, just say "in other words" for the former and "for example" for the latter. It really is important. When I read such dolts (i.e. those confusing the two) I want to take drastic measures (e.g. chew a NyQuil).