I feel that the branding of internet products is somewhat like branding in the service industry: the brand is all about the customer experience and not about the tagline (here's a good article about how the brand is not about the slogan). For instance, it doesn't matter to me if a bank comes up with the coolest slogan, if that slogan has nothing to do with my experience banking there, or if I have a poor experience. In some sense, web companies are also service providers, and if they fulfill a great service promise, they win with users, and they lose if they don't.
In that light, I don't understand how Yahoo! is about me. It seems that they want to latch on to a hot new theme, without doing anything to fulfill the promise of that experience. What do you feel?