Yahoo won't ruin Tumblr, CEO Marissa Mayer says, but Tumblr users are understandably skeptical of that promise. Yahoo has a history of buying popular properties (Flickr, Delicious) and letting them wither away. But Tumblr will change. It has to. Yahoo must monetize the popular platform to justify its $1.1 billion price tag. And you know what that means: More ads.Related StoriesThe 4 Best Things About the Google RedesignHow to capture a sense of speed with panning
