Some random examples – book publishing houses. Or TV networks, in their role as content aggregators (not as producers): TV programming, once an important value-creating activity, is slowly (?) turning into a simple middleman act, as more and more people want to get their content by themselves, and get it directly.

Yes, you can learn as much as you ever need to on your own, if you are motivated to acquire that knowledge. But sometimes you need the structure and steps set out by someone who has already tread that path. For example, I’ve tried a bunch of times to get in shape on my own; working with a trainer and having her help guide me on this path works better for me, because I don’t have enough specialized knowledge of the right steps or where to locate all the information on my own. I will learn and ask questions along the path, but this mentorship is crucial to get me to where I need to go, as efficiently as possible.
Alot of us on the web have figured out ways to get to where we want to be, but since so much of what we do “feels” independent- typing away at our keyboard, not having classroom experiences to learn this stuff- I think sometimes we forget that we have all helped mentor each other along this path as well. We’re in a school without walls, without formal texts, but it’s as much an education as I’ve ever received in formal education.
That said, I wish I had some additional hard core skills built up along the way; the last time I did any serious programming was back in the days of BASIC (yes, you can laugh now) so I know I could learn HTML and CSS better than my at best rudimentary knowledge, but now, slowing down to acquire those skills seems more difficult than doing what I do and hiring that stuff out to others for whom that is a special skill.
Part of it is we can be generalists in many areas and specialists with real depth and breadth of knowledge in fewer areas, and we have to learn when to partner with others to help accelerate our path forward. Getting to the right person is great, but we need to have the skills and knowledge in place to leverage that opportunity once we arrive.
I am a huge believer in gate jumping and questioning the purposes of the gates, but I also know you sometimes have to walk before you can run, metaphorically as well in the Couch to 5K sense.

Traditional credentials like university degrees are like insurance at this point; they are evidence of having traveled a certain path, having a baseline level of knowledge and experience, and the world at large tends to respect that. For example, most people in high public office have at least one college degree, if not graduate degrees. I somehow doubt we’ll be electing a President in the States any time soon who doesn’t have a college degree.

That doesn’t mean that the path to your own personal success requires formal education in addition or in lieu of experience- it’s the mix that leads to the best outcomes. And it depends on your profession as well- I certainly don’t want to be operated on by a neurosurgeon who took all his surgical skill training through twitter.