Initially it seemed to me that ongoing learning in a career was a relatively singular activity-something that those with ambition would undertake to ensure they could attain the increasingly responsible positions that we think of (or used to) as career progression or success. Globalization, acquisitions and mergers and technology have changed the way business operates and will continue to do so, the world keeps moving forward and we need to go with it or get left behind. I will leave the philosophies of being left behind for those that are better able to comment-after all the choice to not move forward in your career development is a real life choice in many cases.
The idea that careers can be lateral growth oriented really serves two approaches - lateral growth provides you with a strong foundation to attain vertical growth or it allows you to do interesting work and have better choices about where and when you will do that work without having to take on management responsibilities. I have observed some very powerful leaders that under our old 'success' models would appear to have a stalled career - yet the reality is they have a lot of power and influence over what goes on in the workplace. When this is focussed it can provide great mentoring opportunities - if you are looking for a mentor consider someone like this - you will learn a lot from them.