I learned a valuable business lesson from my wife yesterday. Annoyance doesn't sell. Even if you think you have an extremely useful product that will improve the quality of life of anyone who uses it, repeatedly telling them so will not help. Customers sell themselves; I only present the products.
As I believe most of my business lessons will teach me how to be a better Christian, I realize that respecting your customers and potential customers is just a variation on "Love Thy Neighbor."