The problem with issue trees is that they multiply dead ends and red herrings. The issue tree structure, unlike what most people familiar with data structures, is unfiltered and has no regard for truth value. False, true, proven, unproven, reliable, fictitious, opinion, fallacy, all are equally valid in an issue tree, and pretty much the only thing that matters to the interpreter is how heavily weighted issues are by visits.
The issue tree is never pruned except by tests of duplication and popularity. Two issues resemble each other so much that the interpreter does not distinguish them (for whatever subjective reason)? They get combined and treated as one. For instance, 100 degree warming in climate by 2070 would for some be no different from 10 degree warming by 2100, so the ‘duplicate’ gets pruned. Ten thousand hits on “cooling by 2050″ vs ten hits on “100 degree warming in 2070″? Well, guess which issue gets taught as a major argument in the controversy to a six year old? Certainly not 10 degree warming by 2100.
Issue trees are great tools for marketers looking for catchphrases and soundbytes to appeal to a demographic. They’re crap for deciding what to put into a school curriculum.
