I just read an interesting article in Mediate.com that spoke the issue of blame--and who's fault it is when a marriage or relationship fails.
Although "blame" is not hardly new territory to tackle, the article made me realize that it's human nature to want to assign blame to a conflict. So, as mediators, we're in the business of going AGAINST human nature to some degree--and asking the parties to do that, as well.
Perhaps that's why mediation's taken so long to catch on--people simply want to be "right" and blame the other party. When asked to work the problem or issue without assigning blame, it's as if we're asking them to sacrifice their first born!
Specifically in marriage or relationships, the emotional desire to blame the other person is strong. Think about infidelity--if one person is unfaithful in a marriage, is that person to take on 100% of the blame? Or can it be 50%-50%?
I think best practice as a mediator is to bring up the issue of blame at the beginning of a mediation and make it clear I'm not in the business of assigning blame to one party or another. That way, the blame game ends before the mediation begins.