This Financial Times blog post about Blackberry's service disruption leads me to create a definition for the term "public relations crisis": any screw-up that you can't talk your way out of. How many times have I said it? You can't communicate your way out of a situation you behaved your way into. (Actually, my boss said it, and she tells me she's quoting Pat Jackson.) In my own words, the best public relations is a well-run organization, which means that even the most skilled PR practicioner can't rescue an organization from its own bad decisions.
That's not to undervalue the role of crisis management and crisis communication. It certainly is possible to make a bad situation worse by communicating poorly. (I'm looking at you, Netflix.) No one would have cared that BP had an arrogant and condescending CEO if they hadn't dumped a ton of oil in the Gulf of Mexico. Which isn't to say that every crisis is an organization's fault -- take, for example, the famous case of the poisoning of Tylenol, considered a textbook example of effective crisis management. It's not what parent company Johnson & Johnson said that is remembered; it's what they did -- removing Tylenol from the shelves in the interest of public safety, regardless of the cause or scope of the problem.
This doesn't argue against giving public relations its coveted and elusive "seat at the table." In fact, it's evidence that an organization's senior leadership needs to include public relations staff, whose proper role is to reconcile the interests of the organization with the interests of its various publics. In short, to prod the organization to do right when its instincts tell it to do wrong.