I just completed an email questionnaire on informal learning and am going to recycle my answers here so I have time to get a bit of work done today.

How do you define "informal learning" in the USA and what rating does it have?

Informal learning encompasses all unscheduled, impromptu learning. Common examples are conversations among colleagues, knowledge sharing in communities of practice, finding things out on Google or Amazon, calling the Help Desk, trial-and-error, reading the manual, asking a friend, copying the behavior of someone successful, or reading a magazine article. Studies find that 80% or more of learning in corporations is informal.



How do you measure informal knowledge and what kind of benefit can be expected of it?

The measure of any form of corporate learning is whether workers are getting the job done. Are customers satisfied with the service they receive? Does the organization fare well in benchmarking comparisons with peers? There's really no test at the individual level.

Where do you see the difference between collaboration and knowledge sharing on the one hand and professional knowledge management on the other?

"Professional knowledge management" is a fuzzy term. I will assume you mean formal, traditional, top-down approaches. Most of the attempts I've looked at are failures. They don't focus on what workers need to know, they don't change with the times, and consequently, they are rarely utilized. Knowledge "management" isn't as important as what David Snowden refers to as "knowledge exchange."

Informal, bottom-up approaches work better because they provide answers at the time of need, are structured for rapid access, contain advice on how things really work rather than how they work on paper, and are continuously adapting to fit new circumstances. The better informal systems offer multiple means to get answers: search, chat, mentoring, prompts, phone, simulation, etc.