Both brands and agencies had similar approaches to buying online video ad inventory. Three-quarters of brands purchased inventory from an ad network, making it the most popular source for those companies. Eighty-six percent of ad agencies bought inventory direct from a publisher, making them the top choice for ad space. But ad networks were almost on par with publishers—85% of agencies said they used them to purchase inventory. The survey also found that programmatic ad buying by both brands and agencies had more than doubled between 2011 and 2013. Read the rest at eMarketer.