In a talk last year at (I think) the business of software conference, PG said, among other things, that business schools are useless because successful business people don't waste their time teaching business in business schools, and instead either run their business or enjoy the fruits of their success (another song to the tune of "those who can't, teach").
His depiction of university professors accurately describes most bloggers.
Here's another take on this: those who are good at teaching, teach and those who are good at blogging, blog. In other words, some people are actually very good at teaching or communicating ideas, even though they may not 'do' them.
In reality, there are good teachers and there are bad teachers (and more bad than good).
Those who are good at teaching, teach implies that somehow teachers are selected by their ability to teach, which is not true. Teachers happen to be teachers for a variety of reasons; but their talent has little to do with the fact that they continue to be teachers.
The case of bloggers is arguably a little different; certainly lack of talent or experience does not prevent people from blogging, but traffic provides at least some objective (if imperfect) measure of success.
But I would expect people who describe the road to world dominance to first document what they really know about it: if they haven't traveled it themselves, have they at least interviewed many successful people? What books have they read before writing anything?
It also occurs to me that while 'bad' teachers can often still hang on to their jobs (I've had more than my fair share), very few bad entrepreneurs can still hang on to a business!
I guess the point I was trying to make was that some people are very good at teaching (or blogging) even though they may not have necessarily done what they teach about. For example, I've had great teachers - politics teachers, English teachers, professors in law school, etc - who didn't practice what they taught i.e. my high school politics teacher wasn't a politician, my university film studies professor didn't make movies, my law school professors were not practicing lawyers or judges (in fact my contract law professor was brilliant yet had only practised law for a year before turning to academia), etc. So it is conceivable that someone could teach or communicate something of value without having the personal experience of practising the profession they're teaching about.
Having said all that, when it comes to someone making grand statements about what constitute the keys to success, etc this may not be something that you can truly and credibly teach purely based on persoaln observations or academic study (as would seem to be possible regarding subjects such as politics, film and law to repeat the examples given above).
This seems more like someone attempting to teach or make statements about what it takes to successfully climb a mountain. Mountain climbing is one of those subjects - to which I would definitely add building a business - that can't really be taught by someone without personal experience. These are subjects where the 'lab' is the real world, so unless someone has been in the real world, they really don't have helpful lessons to offer.
His depiction of university professors accurately describes most bloggers.