Nerval's Lobster writes: Yahoo has agreed to acquire Tumblr for $1.1 billion. As you know, Yahoo is a major corporation with a need to monetize its assets in a way that makes its shareholders happy, leaving open the question of whether it’ll alter Tumblr’s DNA in order to make the latter more of a significant cash generator. But at least for the moment, Yahoo seems content to leave its new property alone. “Per the agreement and our promise not to screw it up, Tumblr will be independently operated as a separate business,” read the company’s press release. “The product, service and brand will continue to be defined and developed separately with the same Tumblr irreverence, wit, and commitment to empower creators.” Tumblr CEO David Karp, who has been known to make some very anti-advertising comments in the past, will remain in place. Even so, anyone who likes Tumblr may have some cause for concern, because Yahoo has a history of making high-profile acquisitions that subsequently implode. Back in 1999, for example, it paid over $3 billion for GeoCities, another blogging network that it eventually shut down after years of failing the update the property. In 2005, it acquired popular photo-sharing Website Flickr, which it likewise allowed to languish and die. That same year it bought Delicious, a popular Webpage-bookmarking site, and did exactly nothing with it. So when Yahoo starts off its Tumblr press release with a promise not to screw things up, it’s a self-deprecating nod toward all that history. New Yahoo CEO Marissa Mayer has been on a bit of a buying spree of late, snatching up startups such as Summly in an attempt to make her company “cool” and relevant.