I hesitated to reply to this because what I'm about to say could be taken as pedantic. However, it is my experience that many people experience a good way of working, apply a label to it and then use that label thinking that it will communicate all of the good things that they intended. This is rarely the case. At some point you see many articles entitled "Why X doesn't work" where they describe a broken version of X and why it doesn't work. The broken version ends up getting more popular than the unbroken version for some reason and there is a general consensus that "X doesn't work and anyone that uses X is an idiot", even though X works perfectly fine if you use it correctly.

With that in mind, "lean" as a principle is organized around the idea that it is better have people request functionality (pull) than for you to imagine what people want and then try to sell it (push). Many "lean" organizations happen to be very good at continuous improvement, but you can be "lean" without any capability for improvement.

"Kaizen" is the Japanese word for continuous improvement. It was introduced to western eyes primarily from the "Toyota Way", which is a lean manufacturing system that concentrates on continuous improvement. It is important to understand, though, that while workers have a responsibility for identifying problems, it is the managers who are responsible for working with the workers to implement improvements in the Toyota way. So there are clear demarcations of responsibility, unlike many of the IT processes that borrow the word "kaizen".

Even "continuous improvement" can be a loaded term with respect to responsibilities. The first time I ran across the term was dealing with CMM (the Capability Maturity Model). Once you are up to level 4 or 5 you are using metrics to improve your process in order to obtain continuous improvement. In every organization I've seen that attempted to achieve CMM level 4 or above, the primary driver was management (and often workers were not even consulted about improvements or why they were necessary -- they were only told to do things a certain way). I'm not saying it was successful, but it was very common ;-)

I guess my point is that if you are lucky enough to be working on a team that does continuous improvement well, be aware that what you call "Lean" or "Kaizen" is unlikely to be what other people call it. You can not communicate what it is you want to communicate using those words alone. If you have been reading literature using these words and believe that if you simple follow a "Lean" system and embrace "Kaizen" that you will transform your organization into one that does continuous improvement well, I'm sorry to burst your bubble. If only it were that easy. Unfortunately, all the difficult problems are people problems and those problems almost always require unique solutions. It can be quite tricky no matter what you are doing.