Yes, that demonstrates my point. For the taco stand operator, it makes sense for him to be monitoring those conversations. But why would I, or any one else for that matter, take time out of my schedule and write about a burrito I ate. I have more important things to do. So its sensible for those building a revenue stream; not so sensible for the other chatters.
I think if you were able to see a breakdown of the twitter population, you would see it's used by business owners on one hand, and people with lots of free time on the other.
On another note, I surprised Twitter wasn't sued by TWIT (This Week In Tech), since they were around some time before Twitter.