The popularity of cross fit can be explained, at least in part, because it promises to cram an extremely effective workout into a short period of time that is easy to fit into ones day using short intense intervals and paired opposition exercises. It is almost presented as a hack to get fit in a small amount of time (and is not, to me, out of place on hacker news).

Setting aside the idea that the culture can contribute to people doing exercises wrong and risking injury the debate over cross fit become about weather short, intense, interval workouts are effective.

Famed alpine climber (and trainer to the stars of the movie 300) Mark Twight was an early proponent of the cross fit style work outs but has since returned to including longer endurance style workouts in his programs. He stated in an article titled something like "There is no free lunch" that he saw initial gains from the cross fit style but that endurance began to suffer seriously after 18 months. [1]

Another great climber/multi sports athlete Will Gadd has a number of posts and articles on cross fit and is generally a fan but uses it between sports specific training and with more emphasis on correct form and less on time. [2]

A balanced conclusion would seem to be that cross fit style work outs are better then nothing, can be effective as part of a large training plan even for serious athletes but that we should be aware of the risks of injury and must take personal responsibility for doing exercises correctly. And should still find time to get out for long hikes, bike rides etc if we are interested in having true all day endurance fitness.

[1] The article has since disappeared from his "Gym Jones" website but excerpts can be found here: http://conditioningresearch.blogspot.com/2008/07/intervals-f... http://www.catalystathletics.com/forum/showthread.php?t=5963

[2]http://gravsports.blogspot.com/2009/11/congrats-to-gm-crossf... http://willgadd.com/injury-and-a-few-crossfit-mods-as-a-resu...