According to comScore, Tumblr scored 13.4 million unique visitors in the U.S. in July — up 218% from the same time last year.
The blog-meets-social-network service has seen its most explosive growth in the past few months, according to comScore’s data, upping its unique visitor count by more than 5 million from April to July.
(Mashable - The Social Media Guideから)

comScoreによればTumblrの7月のユニークビジター数は1,340万を記録し、前年同月比は218%増とのこと。個人的にはこの数字以上に、「The blog-meets-social-network service」という表現が気に入りました。