Nowadays, copying a product takes only a week (of course this time span depends on the type of product). Product life cycles are getting shorter and USP's may lose their value as technology develops. Therefore it becomes more and more important to build relationships with customers that are based on trust because they can not be copied by competitors. This modern approach to marketing is called relationship marketing. Sellers are encouraged to build longterm relationships with their customers to ensure customer loyalty. It takes years of hard work and mutual business to build a strong connection, but it provides a huge competitive advantage.
Mutual trust is a key factor in any relationship. It gets lost if people feel manipulated. As a result, communication breaks down, because the information one receives, can not be relied upon. The connection gets lost and with it the client.
Nevertheless some sellers seem to be trapped in the marketing mentality of the 90's. They use suggestion techniques, that are easy to spot for everybody with a basic knowledge of psychology.
Just one example: The anchoring effect. A price that is set at the beginning of the negotiation, influences the deal significantly. In the past, those who knew this bias, could use it to their advantage. But nowadays many people have heard of it and will recognize it as soon as somebody uses it.
The same goes for NLP-techniques that are used to build rapport by simulating similarity or for suggestions, priming and intuitive nonverbal communication, to name but a few. They may help to close the deal once, but in the long run they destroy the relationship sellers need to build with their customers.