...Consumers in the critical 18-34 year old demographic are hooked on Tumblr, with the average visitor spending 1.5 hours per month on the site. Today, Tumblr hosts 90 million blogs that generate more than 89 million new posts every day. This astronomical growth helped the site soar into lists of the top 10 most popular websites in the U.S. at the end of last year and is attracting significant interest from brands ranging from fashion to finance.