There are more than you know about.
It's a tale as old as time, well, at least as old as social media.
Businesses (or people) want to look legit. They want to look like a big deal when you land on their page. Instead of doing the work and being active in the arenas they want to attract followers in, they take a shortcut and buy them. They are no shortage of options.
See what I mean?
But there are ways to figure it out, both on your own and through other services.
The easiest way would be to use a Twitter Audit, they have similar services for Facebook and Instagram. All you have to do is put in the twitter username of who you want to check out and boom, there you go.
You aim to be at 75% or higher on real followers. Not as much on Facebook but with Twitter and Instagram, fake followers are going to happen. Not a ton you can do about it without dedicating a ton of time to combating them. But if you come across someone at a 75% clip or higher, they're solid.
In full disclosure, below is the Alpha Dog score.
Nearly 90%, that's a good number.
If you see an account closer to 50%, it's a pretty safe bet they've purchased followers at some point. If they are down around 25% (or some are even lower) then you can go ahead and assume pretty much their entire "fanbase" is purchased and artificial. You don't want to see that.
You can check out other ad agencies in the area and get their numbers with a simple click of your mouse. And if you are a business owner, understand that it's not worth it. And if an agency promises you x amount of followers or traffic in a short amount of time, know that they are probably buying it and it doesn't help your business at all.
The more you know.