I've been a host for five years and have almost 500 guest reviews, but have had a couple that have made me want to reconsider my relationship with Airbnb.
These are incidences where a guest clearly did not read the listing details, house rules, or look at all of the photos provided... then gave me a poor review as they were surprised by something when they arrived. I've even been marked down for "accuracy", and Airbnb has sent me nasty-grams about my listing details!
What disappoints me most is that Airbnb doesn't support hosts when this happens. They will not remove bad reviews in this situation, in spite of the fact that there is nothing the host could have done to meet the guest's mistaken expectations. I'm just dumbfounded by this.