The 468x60 banner format isn't dead and can definitely be effective. Just look at PointRoll's mouse-over expandable ads and OnFlow's wild animations. But 468x60 is just not a lot of space to work with. Even with some richness and interactivity, the banner has become predictable and routine.
People know where it is, what it looks like, and how to ignore it.
When you do what everybody else does, you don't stand out. Web publishers are trying to one-up each other in order to pump some new life into the industry and to generate more advertiser value and interest. We've learned that this is a media that can never stand still. Online consumers are savvy to marketing, they get bored quickly and they ignore the routine. A constant flow of innovative and creative ideas is what it will take to bring Web advertising back and to keep it interesting.