“Nanos” for short. From the NYT story:

“People who have as few as 1,000 followers and are willing to advertise products on social media. Their lack of fame is one of the qualities that make them approachable. When they recommend a shampoo or a lotion or a furniture brand, their word seems as genuine as advice from a friend. In exchange for free products or a small commission, nanos typically say whatever companies tell them to.”