I agree that the service is pretty much worthless to normal searchers beyond its initial gimmick-value.

However, if you're looking for niche markets (terms for which getting top rankings might be feasible) it could cut down on your research time. So it could be useful for SE marketers.

I would be surprised if it got out of beta. Of course, you never know. Maybe people would like to see popular terms that others are searching for. I actually learned about a couple new things when I was messing around with it. Also in support for this thought is the fact that Yahoo! now includes a blurb about its 'Buzz Index' info on the homepage.