I can give you guys some input on the whole initials thing, being a practicing RN right now. This is just my experience at my hospital, which is a rather large teaching hospital in a major metropolitan area.
Some of it is just plain old pretentiousness and seen with many nurses looking to protect their ego or show how much "stuff" they know and start an exorbitant and unnecessary amount of post-nominals (MSN, BSN, RN, EMT, CPR, ect...). Seen a lot in newer nurses I've noticed who got a chip on their shoulder who want to show off their shiny new degree or certification and feel that it's the best thing ever. They soon realize hardly anyone cares and it's tacky as hell.
As a clinician, obviously I attach "RN" to the end of my clinical documentation or charting for obvious reasons. I have my badge which states my name and designates me as RN. This is mainly for chart reviews and so people/patients can identify who I am and my role.
Administrators, supervisors, and non-clinicians usually have there name with their RN followed by the level of education, as further education has a lot to do with administrative procedure, healthcare management, and running units. They sign off on stuff with those postnominals as well.
There are certifying credentials like CCRN (critical care), CEN (emergency/trauma) and OCN (oncology) that I feel are appropriate as post-nominals because they are clinically relevant, although I generally hate word spaghetti. As a general understanding, they recognize that specific individual as being top of their game in that department and they have an advanced skill set. The examinations are usually taken after several years of exposure within that field. I think that is is most akin to physicians having fellowship training. Correct me if I'm wrong, I'm not too keen on it.
As an example my complete title is "Vigil, RN, OCN" so others know that I'm not only a registered nurse but also have chemotherapy infusion capabilities which you have to be certified to preform. It's nothing fancy, but an indicator if someone needs me to float to another unit to start chemo and monitor their nadirs, call the docs with critical values, ect... It means that I am the most qualified to do a rapid assessment of a cancer patient when the rest of the floor are normal RNs.
But again, the people who have Jane Doe, RN, MSN, BSN, ACLS, BLS are generally the obese administrators, patient advocates or educator nurses who haven't been on a floor in decades, preform sub-optimally in actual practice, and feel the validate their worth through a slew of redundant letters.
Or their newbs.