A story in Technorati yesterday revealed findings that almost half of all Twitter followers are bots. That can hold conversations. And no, I don't mean yesterday's @sweden account either. I mean actual bots, as opposed to real people.
Brands use the bots to increase their followers in the same way you have to "Like," a brand on Facebook to engage with their shiny new app. It's clever. And the article makes the point that no real value comes from having a a huge follower count, especially one where half is made up of software.
What the article doesn't mention is that your favorite social media ninja guru wunderkind is most likely doing the exact same thing. Beyond being one of those actions that provokes the ethical question "how do you sleep at night," if the so called expert is also one who considers themselves A Brand™, it might technically be violating advertising standards in certain countries, too.
For every high profile person out there with a legitimate number of followers (artists entertainers, and the like) there are also 23-year olds you never heard of, who have impressive numbers, too.
Telling the difference might be hard. So start here If some of them contribute nothing to social media beyond telling you they are good at it, you can assume that that half their followers are made up.