In general guests do not understand the impact of their rating on hosts. Maybe an 'are you sure' button before they hit send LoL. Give people the power to review and its amazing that some think they're writing for a travel magazine and rating a 5 star hotel. I make a point of saying that this is my home and not a hotel to try to plant the seed.
Still, people can be hyper-critical over things that are not worthy of such attention, or even a second thought by most others. Guy booked smaller room, put in in the larger suite and he gave a 4 for value -- what an ingrate and if he'd thought for a moment, or, had any humanity he would not have done that. Petty ... 5's for cleanliness etc. Value 4 - how stupid is that.
Because of their lack of responsibility / consequences and this new rating system its going to hit SH's harder than Airbnb imagines and its simply not fair and you can't appeal an unfair rating / review unless they 'get personal'.