Virtually every business entity and sub-entity, large and small, have customers and vendors. Customers generally expect to receive a worthwhile expertise, product or service from a business. Along the same lines, vendors generally seek to provide worthwhile expertise, product and/or service to a business.

The provision of these products and services at all levels may or may not involve:

A) Either a vendor or customer of the business desiring or actively seeking to harm said business (i.e., the opposite of the businesses best interest)

B) Either a vendor or customer of the business having no opinion or and no interaction whatsoever with said business outside of the provision of product and/or services (i.e., having no interest in the business)

C) Either a vendor or customer of the business intending to help and/or provide worthwhile help to said business (i.e., having the businesses best interests in mind)

It is quite possible that a businesses vendors and/or customers do have said businesses best interests in mind (example C above). Examples A and B are also possible.

Saying that "only -you-" have your best interests in mind is certainly a possibility in some dealings, but my guess that other scenarios are also common.

I agree that it may be wise to assume negligence and double check extremely important matters to a much greater degree than normal. The scenarios outlined in the linked article are a perfect example of negligence, inexperience and lack of communication at many levels. But, at some time, you simply must trust others and can only use your wits, experience and the expertise of even more parties to ensure that those involved in your dealings are doing what they should to the highest professional standards.