Basically as on date the free listing companies are attracting business people to list their businesses on their portals. Their strategy behind free ads or free adverting is that they want more and more business listings on their portal.
However, it is in mutual or say give benefit to all including – publisher, business people and the end user or the customer.
As soon as a business is listed on a portal, it is automatically displayed in google searches but all these businesses are displayed through the portal where it is listed. In this way, the portal got ranking and the business people get business promotion without any payment.
Hence, it can be said that free business listing or free ads gives mutual benefit to the publisher as well the business people.