It would be more interesting if Twitter showed local trends, such as the trends in Tweets by people in my city, or in my neighborhood, or even on my block.
Spectacularly useless may be an overstatement. Even if the twitter topics reflect the mass-media-consensus at the current time, they could still serve as an indicator of a topic being repressed in the media while spreading through new media.
Once a service crosses a certain threshold they stop being cool and start reflecting the masses. Look at YouTube now, its MTV + America's funniest home videos (minus Bob Saget).<p>Facebook mainly beat this by being a <i>very</i> walled garden. Oh-so-open twitter can't do that. And for the record FlockingMe didn't seem any more relevant than the masses just my friend's drivel.
I agree that trending topics is no longer "trending" simply because Twitter has become "mainstream" more or less. Remember when Facebook wasn't mainstream? Now it's a spammer's dream.<p>So goes any well guarded secret that gets let out. It's inevitable.