I hadn't heard of the term "follower factory" but I have certainly come across the product of them over and over again. Paying for followers on social media isn't a sustainable strategy. Whilst it will make you look popular in a short space of time, it won't do much for your influence.
This latest investigation in the US is based on the fact that "impersonation and deception are illegal under New York law". So called "follower factories" have been set up so that people can effectively pay to boost their follower count. A short-term fix if what you're after is popularity.
As social tools become smarter they sniff out the fake from the authentic. Tools like Onalytica don't just look at popularity, they look at the follower profiles of accounts and check if they really are the right kind of people you need/should engage with.
If you're serious about building authentic influence around your expertise, I say take it slowly, build a quality audience that is truly interested in what you're sharing.
The New York Times published an in-depth report on Devumi on Saturday, including interviews with people who alleged their account details and profile pictures had been copied to create realistic "bots". It is alleged that others who wanted to increase their follower count, including actors, entrepreneurs and political commentators, could then pay to be followed by the bots. On social media, high follower accounts boost influence, which can impact public opinion, or bring advantages, such as job offers or sponsorship deals, to account holders. Mr Schneiderman said he was concerned that such "opaque" operations were undermining democracy.