And back to the principles. As stated many times before, yet seems to be glossed over, is the fact that ALL of us are different (height, weight, bone structure, muscle fibre types etc etc). The Bell curve works, I guess, as an analogy. Most of us will fit somewhere in the middle.
I for one have wasted countless hours in the gym following one program after another (mostly high volume, muscle-mag type regimes). Reason being: I did not stop and think about what I was doing, and what was going on physiologically before, during and after a workout. Bottom line, I did not think critically or rationally about exercise. Whatever the flavour of the month was.
Until I drank the High Intensity (Mike Mentzer, Arthur Jones, Dr. Ellington Darden, Brian D. Johnston) or HIT KoolAid and realised that some very smart people approached exercise from a medical/scientific (ie rational) point of view, vice simply saying "Do this and it will work for you, because it worked for Schwartzenegger or BUD/S Top Candidate X". Here is a quick link to one of the articles that explore the myths and facts about bodybuilding/strength-training programs.
http://www.exercisecertification.com/books/Excerpts/Rational%20Strength.pdf
Whatever program or "bad-wagon" you jump on, stop and think about what you want to achieve (bodybuilding vs ultra-marathon or something in between) and realise that exercise has to be prescribed (as someone posted earlier) to suit the goal AND your unique physiology (metabolism, starting strength, recovery ability, existing injuries/limitations, other stressors in your life). Simply stating "I tried routine X for a month and it didn't work for me" is something we hear too often (not to mention getting tired of "preachy" advocates.
Regarding CrossFit or whatever you want to call it, same applies. Think about your fitness end-state (if there is such a thing) and your unique attibutes. Think critically about the scalability of the system as well as the "prescribed" number of reps/sets (ie volume) and workout days (ie frequency). The WODs given are examples or suggestions, not "presciptions" and are maybe good benchmarks for testing - they do seem arbitrary though come to think about it. Those of average to below average recovery ability (myself included) have to realise that unlike some people with greater genetic potential, we have to be more careful about overtraining. Maintaining a CrossFit regime (3 on 1 off as "prescribed") with the high volume of work required per workout is just too much, personally (from personal experience with high-volume training). To someone else, maybe the perfect fit. I could easily do this for a month or two, hit a plateau and actually start losing muscle/energy, and dismiss the program/routine as bogus. No, the basic premise of the program (eg. achieve and maintain well-balanced fitness) may have been sound (and achievable), but the methodology may have been flawed due it not being tailored to the individual.
Personally, I have found HIT (properly applied) has worked the best for me over time vice the high-volume/periodization approach. However, I have begun to substitute CrossFit-like activities (at moderate intensity) as a way of getting away from the overly linear and mechanical lifting demanded by HIT (one set per exercise to momentary muscular failure back to back, no more than 10-12 exercises per workout). Having done some of the CrossFit routines so check for baseline muscular endurance, I have found that HIT actually benefitted me and the results were good. Again, I have to rethink the whole intensity/frequency/volume equation to ensure I consistently achieve better results every time I work out while staving off the beast known as overtraining.
I have gone on a rant about this on other posts, but seems like the same themes are being brought up here, with everyone tap-dancing around the core principles. Bottom line - before trying to sell ANY program/routine/system as the be-all-end-all, think about it first (requires more work at the front-end, but will save months if not years of frustration and shooting in the dark).