@Sitara3
Yes, all the time. On my tiny two person max unit (no extra guest fees) I would say probably 30% of my guests do not select the correct guest count (defaulting to one guest instead of changing it to two.) It is not malicious, they just overlook it.
I think that Airbnb can address this problem by having the guest count default to zero. The guest would have to input the number on on their own and take full responsibility for it. If the guest count came through as zero then obviously we would question it.