Dive summary: 

• Social bulletin board Pinterest is finally, after four years, experimenting with advertising by launching promoted pins. 
• The initial promoted pins will start with the search feature and the category pages—searching "Halloween," for example, might bring up a local retailer's pin promoting a costume sale—and the selected brands won't have to pay for them, as Pinterest wants to work out any bugs. 
• The platform plans to do extensive research to find the right balance between ads and organic content that is tasteful, transparent, relevant and improves based on feedback, providing value to advertisers without turning off users.

From the article: 

... To that end Silbermann defused fears, writing "I know some of you may be thinking, ‘Oh great…here come the banner ads.’ But we’re determined to not let that happen." ...