Ever since I joined Twitter, my account has been bombarded with tweets on informal/social learning. If you don't know or you need a quick refresher on what informal learning is read What is Social Learning? Is this a new type of learning? The answer is a sure no. Informal learning has been around for ages, even before formal training came into the picture. People have always been exchanging notes to perform better.
Read more about this on my latest post at Learnability Matters: Informal Learning - 7 reasons why organizations must promote it