That is Erik's interpretation for its inappropriate use in a forum like this.

Actually, SMS is the GSM^[1] Short Message Service - ie, Text Messages.

Of course, when you're writing a Text Message on a real phone you have to struggle with having up to four letters on one button - so its perfectly reasonable to abbreviate heavily in that context.
But there is no excuse for it - other than pure laziness - on a proper keyboard!

PS

Do you have to be called Andy to join in this Thread...? ;-)


[1] GSM = Global System for Mobile comms