There is not only a burden of proof placed on accusers; there is also a standard of proof. Whereas a burden of proof dictates which party will lose if it fails to rebut the operative presumption, the standard of proof dictates how much evidence must be presented to rebut the operative presumption.
Absent perfect information, a strategy of punitive deterrence requires that some people who are wrongfully accused be sacrificed to deter more crime.
The infliction of harm on the innocent should provide a powerful reason to hesitate before embracing a strategy of punitive deterrence.
The subjectivity of severity. The cost any particular criminal attaches to a sanction is thoroughly subjective. Each person is likely to value the threat of a particular sanction differently—or at a minimum, there is no way to know just how great a cost any particular sanction will impose on any given person. For some the humiliation of a criminal conviction would be a massive punishment; for others even extended incarceration is not perceived as onerous.