There are many style guides[0] that treat i.e., e.g. and the other Latin abbreviations specially in always punctuating them - it's rather rare to find someone talking about the former U.S.S.R., T.C.P. packets, or N.A.S.A.'s missions to the I.S.S. - to all intents & purposes, ie is the exception, not the rule. It's worth pointing out that i.e. is exceptionally difficult to type on a lot of mobile devices.

[0] http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style#Abbre...