There are many little professional cliques in photography. The various brand name "professional services"; and the memory card makers also have their professional cliques as well.
It's not so much about the branding that's important but how these "professionals" push their equipment to the next level.
But Lowepro Preferred Photographer is for everyone who has ever touched a camera who treats it as a serious profession or hobby. It may not be as influential as a Nikon Professional Services acclamation but it's nice to have a little tag that kind of makes you stick out from the average snap-clicker.
However rest assured, I'm looking at getting into the Nikon Professional Services clique. I just need another professional body. Evidently my D300s classifies as one body. I also find that I need two professional lenses. My 70-200mm f/2.8 VRII classifies as one. So I am 50% short of the equipment requirement. I do work as a fulltime photographer. I'm just not "classified" as PROFESSIONAL yet as I don't have a body of work that I have sold very much of. In order to claim classification as a professional photographer you have to be doing this profession full-time and be making money at it. However as I gather my lenses that I need for classification, I will develop a body of work and start submitting to magazines and other publications and looking for print sales. And hopefully in the next few years I will achieve Nikon Professional Services.
If you shoot Nikon and are a professional photographer, check into Nikon Professional Services NPS Membership Info