Blameless postmortems work phenomenally at Etsy which is a pretty low risk setting (after reading Sidney Dekker's book The Field Guide to Understanding Human Error [highly recommended] I would say that blameless post-mortems are even more important in a high-risk setting). Except failure isn't the correct word - the book makes the case that these are natural artefacts of complex systems.

1: https://codeascraft.com/2012/05/22/blameless-postmortems/

2: http://www.amazon.com/Field-Guide-Understanding-Human-Error/...