Exactly. Listening to only loud people in an isolated echo-chamber is a great example of listening to the wrong people. Especially when those people might not even be your customers.

How does it work? People actually choose to follow Tropicana? Or, more generally, how's Twitter valuable for marketers if in order to deliver your messaging you've got to persuade your customers to "follow" you first?

Why would I want to follow Nike or even BMW?

P.S. Perhaps I'm just an 'untwittery type' - I find it hard to believe people actually use Twitter, period. I've tried and my response to 99% of tweets has always been "why would I care?" - if you're into assembling random facts about lives of strangers, just watching them in a cafe or on a busy town square is way more fun.

It looks like @tropicana isn't even owned by the brand. Most likely, they searched twitter for "tropicana", as many brands seem to do. If the company replies to the user from another account, it should show up even if that user is not following @pepsico or whatever (depending on the user's options).