Yahoo! announced Monday morning that they have agreed to pay $1.1 billion (cash!) for Tumblr, a six-year-old online blogging service.

Since she joined Yahoo! last July, CEO Marissa Mayer has acquired several companies that appeal to younger audiences, including Summly, Astrid and Jybe.  I think this acquisition definitely comes as another one of Yahoo’s attempts to make itself more relevant among young people, and in order to do that, you need to have some sort of blogging platform.  In addition to making the announcement of the acquisition, Yahoo promised not to “screw up” the relationship.

Tumblr is an online blogging site that lets users share just about anything-text, photos, quotes, links, music, and videos from a browser, phone, desktop, email or wherever they happen to be.  The site has over 108.8 million blogs and over 50.9 billion posts.

For those who are worried that Yahoo would alter Tumblr’s edgy image, Yahoo said that Tumbr will operate independently as a separate business.

“David Karp will remain CEO. The product, service and brand will continue to be defined and developed separately with the same Tumblr irreverence, wit, and commitment to empower creators,” the statement said.

David Karp, Tumblr’s 26 year old CEO, also seems happy about the acquisition, blogging “Before touching on how awesome this is, let me try to allay any concerns: We’re not turning purple. Our headquarters isn’t moving. Our team isn’t changing. Our roadmap isn’t changing. And our mission – to empower creators to make their best work and get it in front of the audience they deserve – certainly isn’t changing,”

What do you think of Yahoo’s latest acquisition?  Let us know in a comment.