I think it would be very worthwhile to ascertain how much online reviews on the modelling fora influence sales amongst the wider modelling fraternity. I think it probably has a great influence. I think issues over buildability probably outweigh most accuracy issues, but those do play a part if you have a choice of 3 kits of the same type.
I no longer buy kits (except WNW) until I have seen one built. The new G50 is one example I cannot find a single completed kit on the web.
I think for smaller companies with enthusiastic modelling staff, adverse critique does hurt. The larger companies are happy if they sell X units and any over that is a bonus.