In general, I agreed with the author... people don't tend to know what they might want to be doing later, and what seems like a good idea now might not be down the line. It's ridiculous when job interviewers ask what we envision ourselves doing in five years, and I have no idea what kind of absurd things I've made up when asked this question. I mean really, surely they didn't want to hear that I envisioned myself far from their boring rent-paying job and was hoping to have a good book contract lined up within five years (OK, I may have admitted this to a select few interviewers who were clearly intelligent enough not to take it as an insult).
At the same time, some of the comments made excellent points in favor of planning. It's important to know your interests and aptitudes, and of course certain types of work require considerable education and training. Just because I once envisioned myself becoming an archaeologist, paleontologist, AND astronomer does not mean that I continued to suppose this was possible once I had passed the age of ten or so. The notion of being a ballerina, fortunately, was routed from my brain even earlier when I quickly discovered I had no aptitude whatsoever for ballet and that it was not really quite what I had imagined it to be.
I like to think, however, that most of us have aptitudes for quite a few things, and this is where the career-planning issue comes into play. One has to at least think about the matter now and then, but obsessing about it seems rather fruitless. The main thing seems to be to come up with something that will be reasonably interesting and pay the bills, or else that something that pays the bills has to be found to subsidize doing something more interesting.
And there you have my life's career-planning wisdom in a nutshell. Initially I stuck to the second strategy, now I'm giving the first a try. I don't think one is better than the other, but after awhile a person gets tired of all those low-interest, low-pay jobs (even when they are punctuated by some higher-interest, equally low-pay jobs). If people are willing to pay me for doing something relatively interesting, who am I to say no?
And now back to petting Ms. Spots.