An ad-tech startup that turns ride-sharing vehicles into digital billboards just raised $21.5 million Posted on December 9, 2018 by bm11c https://www.businessinsider.com/firefly-is-turning-ride-sharing-vehicles-into-digital-billboards-2018-12 Share this: Share on X (Opens in new window) X Share on Facebook (Opens in new window) Facebook Like Loading... Related