Well yeah, but that's 20/20 hindsight, isn't it?  Who gets a survey done to buy a residential poperty, unless they know there's some issue already?  Do we really want people to feel like they have to get a $400 survey before they buy a home?  While you are correct that a survey probably would have saved these homebuyers a lot of grief in this particular case, this seems to be an unnecessary extra expense in the general case.  For that matter, the issue could have been easily solved for free if the homebuyers had gone to the County Planning and Land Use office and checked for pending code violation notices, but what homebuyer would think to do that?