Let's start by clarifying the question, by asking more questions.
Do instructors need to adapt to Long Tail Learning?
What's an instructor's traditional scope of learning?
Is an instructor's ultimate role to help students or teach certain content?
I think Long Tail learning is a fact of life that cannot be ignored. We could choose to not acknowledge it but that would only serve to marginalize ourselves. The long tail is the way things work, and we must embrace it. A learners attention is split in so many different ways. Our tools now embrace this through RSS, and other cross-linking capabilities. Now our methods and approach must also embrace it. When classroom discussions go off on a tangent it might be impractical to enable it. There is material to cover in a fixed amount of time. A skilled instructor might be able to direct the discussion back on point but it’s a tight-wire act.