Actually in a way they are all wrong. Somebody who writes "PIN number" is not writing "Personal Identification Number Number", they are writing "PIN number". Through their use acronyms acquire an identity of their own that replaces the original meaning, usually to the point where few people know what they once stood for. LCD was perhaps originally an acronym for Liquid Crystal Display but now "LCD" has just become descriptive of a type of display, like OLED, plasma or TFT.
You should, argue the language mavens, just say ATM, PIN and LCD. But the weakness of this approach is that you lose the valuable redundancy of "PIN number". Sometimes redundancy is considered bad but it is actually essential for effective communication. You could conceive a code-based language where there is a character string for each idea. It would be extremely compact but very vulnerable to errors -- just like commercial codes in the telegraph age where a single mistyped letter could literally spell disaster.
Natural human languages are highly redundant but the extra symbols you use to communicate help understand the message when part of it is lost or garbled. Suppose I say ATM and someone coughs at the same time. Quite likely your brain cannot recognize the sound that you hear. But when you say "ATM Machine" even when part of the sound is corrupted my brain can still recognize what you probably said. The redundancy also speeds up understanding because recognition is faster when your brain has fewer choices. There are many sounds that are similar to "ay-tee-em" but few that sound close to "ATM machine". Many acronyms are also used for different things, so adding that extra word avoids confusion.
So on the one hand communication experts will tell you that the redundancy makes your communication more effective. On the other hand writing purists will tell you that it is "erroneous" or "a common mistake". Yet you can't ignore them, because maybe among them are your boss, your best client or someone you hope will hire you. In cases like his when you have to choose between two unattractive alternatives the best idea is to choose the third -- in other words to find a new alternative that is acceptable to everyone -- what I call a "third of two" solution.
In this case the "third of two" solution is very simple: use redundancy for good communication but avoid using the same word that was used in the acronym. For example, you can replace PIN number with PIN Code -- most cellphone makers in fact do this. Instead of ATM machine you can say cash machine and instead of LCD display you can write LCD screen or, better still, Liquid Crystal Display. Very often acronyms are unnecessary anyway.
Looking towards the future, though, anyone who creates a new product, technology or service might help to avoid this kind of problem by coining terms that can be abbreviated gracefully, perhaps even recruiting a professional writer to help them. By thinking about these issues upfront you can make life easier for everyone else.
Lecturees, Workshops, Coaching & Writing
For lectures, workshops, coaching and writing on this an other communication topics visit http://andrewhennigan.com, email firstname.lastname@example.org or call 0033 6 79 61 42 81.