This article brings up an interesting issue and one that applies to MDs as well: what are the limits of how a physician or other practitioner can represent his or her practice? Setting aside the NP debate for just a brief moment, we all know MDs who practice well outside their scope of training. I personally know of OBGYNs doing plastic surgery, ENTs who do breast augs, and countless specialties doing Cosmetic procedures for cash paying patients. Generally speaking, hospital credentialing prevents much of this crossover in more traditional settings and certainly within academia, but there aren't many restrictions on what you can do if you just hang your own shingle and don't overtly lie about your credentials. Apparently malpractice isn't cost-prohibitive either, and I've been told that they are legally more insulated because of the entire definition of "standard of care," namely as the care given by someone with "a similar background and in the same medical community."
For whatever reason, licensing boards haven't seen fit to take aim at docs who step outside their specific area of training. Just like with the OPs article about the peds NP, patients generally can't tell the difference unless they know what to look for and what questions to ask. The medicolegal side won't protect patients either given the definition of standard of care mentioned above. Standard of care for the NP in the article is the level of care given by a similarly untrained nurse practitioner practicing in a general community practice.
I don't think the answer to these issue lies in legislation. We're all old enough to have witnessed legislative bodies at all levels of government continually screw the pooch when it comes to something as complex as healthcare. I don't think nursing boards are going to be any better at restricting scope of practice than we MDs have been with policing our own.
I think the answer lies in accepting certain aspects of this battle as already over, and focusing our efforts on educating patients and finding ways to demonstrate to the public that we physicians do indeed provide a superior service. Perhaps a national ad campaign with a tagline like "always ask to see a real doctor" or "when it comes to my daughter's health, we will only see an MD." [sorry DOs, you got sacrificed upon the altar of cadence!]