The notion of informal learning is always going to be appealing, because there seems to be such a strong correspondence between informal learning and deep learning. A while back Graham Attwell was discussing definitions of informal learning. On the whole, I don't like overdwelling on definitions, but whenever I've read about informal learning it has always bothered me what exactly it means and where exactly you draw the line between formal and informal learning.
However, a sensible definition recently occurred to me:
The degree of informality of learning is the degree to which you haven't been told what to do i.e. informal learning by definition can only be influenced by creating an environment and not by direct instruction.
There are obviously different types and levels of being told what to do - based on contractual agreements of various degrees of formality as well as social conditioning.
Going to a lecture because I've been told to by my university because there's an attendance grade, is different from going to a lecture because the university has told me it might not be a bad idea if I want to get a degree, which is different again from going because a friend told me to go because she thought I'd find it interesting.
I may be taking a degree because society has told me I need one to get a job that will make me happy, or I may be taking one because I've been told it leads into my dream career, or I may be taking a degree because I'm just interested in the subject.
Of course deep formal learning often occurs when there's a strong alignment between what somebody wants to do and what they are told to do, so the fact they are being told to do it becomes less relevant. Luckily there are quite a lot of things that people do like doing such as listening to stories and doing the things that make games funs to play. Also allowing people choice of what to study means that they'll hopefuly filter according to what they like doing. Most of us have also learned to think long-term rather than short-term too.
When I was convalescing from flu from the other day I listened to Paul Graham's talk at OSCon
One point he made was this: "Well it's true the benefit that specific manager could derive from the forces I've described here is pretty much zero. When I say business can learn fom open source I don't mean any specific business can I'm saying something less optimistic. I mean business can learn from open source in the same way a gene pool learns about new conditions. I'm not suggesting companies can get smarter, I'm saying dumbs ones will die".
I think a similar thing applies to learning - there's not necessarily any benefit a specific teacher can derive from informal learning, but if the networks for informal learning improve, then the business of education will change.
Software development and education are both businesses that can be personally rewarding to be in - creating software and teaching people things are satisfying pursuits. And that's why this evolution might well be possible. But in the same way that open-source only really works with certain sort of software, I guess the same could happen with education.
There can still remain a market for education that needs to be geared to a specific audience (c.f. paying for support or customisation of OS software), that is slightly boring to deliver (c.f. you don't get open-source banking software), for areas where subject expertise is rare or expensive (c.f. specialist software) or where there's a monopoly in assessment that comes packaged with the education (c.f. software running on hardware other than a PC).
Interestingly I think language learning is an interesting example of when formal learning becomes useful. Expertise is genuine - I want a much better Chinese speaker than me to help me learn Chinese rather than someone else who is also learning at the same level. I want someone who can correct my pronunciation and spot the weird mistakes I make.
I have done informal language exchange stuff and it's been rewarding but I've also been lucky being relatively unusual as an English speaker who wants to improve their Chinese whereas Chinese speakers wanting to improve their English are very common. I've always had to turn lots of people down. But even with that, I've found it takes some effort to work and it's hard work - both people essentially have to become good teachers.
And maybe that's what it's really all about - teaching everybody to become a good teacher not just the few people with that as their formal job. Maybe that's what we should really be teaching in schools.