How can a Bitcoin consumer and a Bitcoin seller mediate disputes? Since Bitcoin payments are non-reversible, what technical and business solutions are there to mediate issues such as


Product wasn't as expected
Payment was double spent or in an invalid chain
etc...


Right now it seems that these issues are fixed by "having a service on top of Bitcoin" and these mediators use their own opinion to mediate the transaction.  

The problem I have is that these mediators may be biased for the seller, or the buyer and may not be publicly accountable (or audited) for their decisions.

Question

What solutions exist (no matter how imperfect they are) to address product disputes when doing transactions with Bitcoin or other Virtual currency?
I'm a mediator and this is an interesting subject. In the conventional world it's seller beware, as the customer can either not pay at all, or charge back a credit card. In the case of Bitcoin, the situation is reversed, and payment once made is gone. I don't think that the issue is with the bias of the mediator, most are neutral, but I do think that a mediator can help to assess the intentions of the parties and a clear path to resolution. It all depends on the intentions of the parties and their willingness to correct whatever is not right about the transaction.  A good mediator can point the way forward in that discussion.