And the site doesn't really shy away from that fact, acknowledging as much in its community guidelines.
"Tumblr is home to millions of readers and bloggers from a variety of locations, cultures, and backgrounds with different points of view concerning adult-oriented content," the entry reads, asking users only to make sure to identify such pages as NSFW ("not safe for work") and, of course, not to post anything illegal.
That's all well and good for an edgy startup, but could be an issue that needs to be tackled as Yahoo aims to appeal to as many advertisers as possible.
In the meantime, just make sure you look for those four letters when searching the site.
For a few years, nobody's really been sure what Yahoo is, other than a place where an aging user base gets its e-mail and looks at a few news stories.
Tumblr is Mayer's bid to get young and hip -- and it's not a bad bet.
From "Sh*t My Dad Says" to "Reasons My Son Is Crying," the most buzzed-about blogs of the past few years have tended to originate at Tumblr.
Whether its "Kim Jong Il Looking at Things" or "White Men Wearing Google Glass," fun and a little bit edgy isn't hard to find on the site.