I would tend to disagree with this blanket statement.
We are a dropshipper, however we have an indepth knowledge of the product. We even have uses and recomendations regarding a product that the manufactuer or distributer does not have.
We handle all the functions of customer service. The only thing we don't do is ship the product.
The reason we did this, is that it reduced the cost for the customer, reduce the chance of a backorder, and speed up the delivery time. It does not make sense for the distributer to ship the product to us, so we can turn around and ship it to the customer.
I belive that Full Service Business (without the shipping department) is the wave of the future.
We don't tell the customer that we drop ship, because its part of our internal business model. We don't consider it deceitful, as it has no impact on our customer, and we don't want to give away to much information to the competition.
The customer wants excellent customer service, knowledge about the product, and fast delivery. They don't care who actually ships the product.
A dropshipper that provides no or poor customer service, should be considered an affiliate.
If a DMOZ editor is unsure, if to add a dropshipper, they should call up the toll free customer service number, and see how knowlegeable the staff are. This will quickly tell if the dropshipper is worthy of a listing in DMOZ.