It's a mistake to think that this whole exercise was about changing the logo. Mayer has inherited a demotivated and dispirited team of developers and designers that she has to forge into a company capable of competing with Google.
One of the things that she can do to motivate her teams is to take an interest in what they are doing - a weekend retreat for the design of the logo? Great! Marissa cares about what I'm doing, I'm important to the company!
On the other hand, having your CEO show an interest in what you are doing is generally speaking a huge motivator for people. It's cold indifference to anything you do that will drive people away.
I'm willing to bet that the actual target for the logo redesign story was internal. Mayer is sending a very clear signal to all Yahoos that yes, they are good enough, and no, she isn't going to get external help to do the things that are core to Yahoo's business.