"Agile is Simple" I keep getting told by the evangelists and of course, in concept, it really is. The trouble is that it's human nature to want to "know things" with certainty. None of us really like anticipation. Oh I agree it's exciting but given a choice between "knowing now" and "knowing at sometime in the future" we'll always pick NOW.
There have been a lot of studies to do with Stress and, without fail, they all show that ambiguity and uncertainty are top of the list. So it's little wonder that when "Product Owners" and "Developers" aren't properly collaberating the whole "Agile thing" becomes more complex and frustrating.
This short video makes the point much better than I can. Enjoy!
Another SCRUM Perspective