You've fallen into a common statistical trap. If we assume the volume of auto-generated spam is significantly (several orders of magnitude) higher than the volu

You've fallen into a common statistical trap. If we assume the volume of auto-generated spam is significantly (several orders of magnitude) higher than the volume of legitimate reviews (which seems to be the case, and would make sense), having a 99.999% success rate doesn't mean that users will observe 99.999% legitimate reviews.