I think that finding fair value is something that is a bit of a comfort to buyers but has nothing to do with whether the seller will accept an offer or not. Subsequently using a tool like zillow to establish fair value is inaccurate at best. Knowing details about the comps that you are selecting is just as important as the chronology of when those sales occurred. Knowing other issues such as expireds, cancelleds, and active pending ratios in the submarket you are thinking about is just as important. The active pending ratio is crucial because the comps may say one thing with respect to the price but have no reflection of the current activity. Thus you may base your offer on those comps but if the area is active your offer will be bypassed. Value is only an opinion that is nothing more then a snapshot in time. I am not saying it is not useful, but don’t bet the farm on it.