Who cares that it's from someone promoting their company? They're giving data that a lot of people are interested in, that hasn't been put elsewhere. The fact that it's better, more thorough data than other places also shows that there just might be a better source out there for gathering data (ie RJMetrics). Everyone wins.
With any of these social platforms there is a small percentage of creators and a large population of consumers. For example, look at Youtube. The same can happen for twitter...a lot of people may just consume the tweets of celebrities or other feeds. Low tweeting is not a big issue. The consumption traffic continues to grow
Low tweeting is a big issue, since it negates some of the Twitter narrative. The whole "pulse of the planet" realtime search thing isn't really valuable if most of the users aren't contributing to the corpus.
Also, if it's just a handful of the users creating the value, then the switching costs are much lower. You'll go to "where the celebrities are" (which may turn out to be Facebook, or something else) and not the harder to move "where are your friends are".
Not to be a broken record, but I think these accounts are setup to "listen" to the brands, people, celebrities, products, etc that the subscriber is interested in. Most people don't blog, but lots of people read blogs. Twitter isn't really a social network, it's a subscriber broadcast medium.
Not exactly - twitter, unlike facebook, is asymmetric, so you expect a large percentage of users who are just listening. That doesn't mean you can ignore them - they are the audience.
