What Yahoo! is trying to do with Tumblr is like throwing darts at the wall, but maybe something will work.
Andrew Nusca and Erin Griffith capture in a nutshell my take on Yahoo! CEO Marissa Mayer is burning a lot of cash in buying sprees, but doesn't seem to know what will actually work. That's not necessarily a showstopper, because after all Google needed a few years to figure out how to profitize YouTube, when it made this acquisition. But I don't have the confidence that Mayer, a former Googler herself, knows what she's doing or, if she does, has what it takes to do what she needs to do.
I think part of the problem is that she's taking a copycat tact with growing Yahoo!, instead of blazing new trails via innovation. If Griffith is right, then pursuits of Dailymotion and Twitch, as so to have a YouTube under her umbrella, were pathetic efforts. In one interview, she did acknowledge that some of her acquisitions were more for the talent than for the platform or product. That's a good thing, because it positions Yahoo! to invent better darts, new boards, or an entirely new game.