Source: Karl Wüst & Arthur Gervais, "Do You Need a Blockchain?" Crypto Valley Conference on Blockchain Technology (2018)
The threshold or gateway issue when approaching the debate around blockchain use cases (particularly, non-currency use cases) is whether a particular problem is "suitable for" blockchain intervention.
Wüst and Gervais provide a simple flow chart to assist in crossing the threshold issue centered on the concepts of (a) state, (b) root access, read/write, (c) trust, and (d) system robustness.
N.B. Above, I use the phrase "suitable for" instead of "requiring of" in order to pay respect to Amara's Law (see Field Note 10, On "Amara's Law + Exponential"); it is my bias toward positive optionality and humility before the phenomenon of technological emergence.