[dragonwriter]

Approval Voting is problematic, especially in a multicultural electorate, for situations where there is not a concrete definition of the meaning of the approval threshould, because different people interpret "approve" differently (it's basically asking the to impose a binary threshold on a continuous-but-not-consistently-quantifiable value), so it suffers problems from inconsistency in input data. The impact of any individe all voter is small enough and hard enough to viscerally percieve that there is no strong feedback method to, over time, align understandings of "approval" so the meaning is consistent across ballots.

Approval Voting is not problematic for situations where you don't need ballot secrecy and approving is, e.g., a binding commitment to participate if the approved option is selected (or where non-approval is a binding opt-out), or where some other consistent concrete consequence of approval exists.

A similar problem exists with most numerical rating (as opposed to ordinal ranking) methods, and to other ranking methods with smiller number of rankings than alternatives, and, perhaps, to a much lesser extent, to ranking systems that allow (but don't require) equal rankings.

Because most analyses silently assume a consistent the mapping from an internal utility function to ballot marking, this is frequently overlooked.