Blame can hurt a negotiation
When confronted a great-white without your spear gun, don't waste time dwelling on who forgot to pack it.
Blame is something we do to make ourselves feel better about something bad that has happened. Usually we seek to blame someone else for something that has happened to us. Blame may be comforting psychologically but it does not change the reality of what has happened.
In an argument or negotiation, casting blame heightens tempers and causes embarrassment. It does not help resolve anything.
If you blame a third party, you merely reduce your credibility. If you blame the other party, they will likely stiffen their resolve. At the very least, they will be unlikely to want to cooperate with you.
Blaming is an attempt to displace guilt. It is not an attempt to resolve a situation. Don't get caught up in the blame game if you sincerely want to find a viable accord. People granting concessions from guilt don't really want to do so. As with any coerced concession, they may later change their mind.
While casting blame is often a useless exercise, there can be situations that call for assessing blame. When a mediator conducts a mediation session, he does so as a arbitrator between upset people. One aspect of the mediation process that makes it effective is that the parties are provided a chance to confront each other directly. They get to say all the things about the other person that have been festering since the legal process started.
An adept mediator will seek to get both the facts and the feelings on the table at the beginning of the mediation session. In many instances, simply being able to confront the other person relieves so much of the frustration that the mediator is then able to start the constructive process of rebuilding trust between the parties. Often a settlement is not possible without this airing of feelings.
Blame can be used as a tactic in negotiations. Don't be afraid to take some of the blame. Taking blame can create an empathetic environment from which collaboration can emerge. If a discussion is heated and at an impasse, taking blame for some aspect of the difficulty often results in the other person recognizing your attempt to take responsibility and eases the tenor of the argument. If there is a misunderstanding, assuming part of the responsibility for that misunderstanding can diffuse an otherwise tense, non-productive environment.
Be sensitive to the climate of the negotiation and don't be afraid to intervene to improve the situation. Your ego is a small concession for a major gain.