That is something I do not practice on my blogs.
From day one, having not a single subscriber, I decided not to go for the 'follow me and I'll follow you' tactic of garnering readers. Why?
Because I do not want to follow a blog I will not read, nor do I want someone to follow me but not read my content. Whats the point of having millions of subscribers but none of them will take the time to read anything you have written?
If you honestly want to know if you are interesting, and if your content is captivating, then practicing 'sub for sub' will not help you grade yourself.
To be honest, this blog only has one subscriber. And that does not bother me at all. I know personal blogs are boring to the general audience, so why bother doing 'sub for sub' when no one cares about your personal life?
My other blog on wordpress however, has grown in subscribers since I started it, and not a single one of those who subscribed were out of that practice.
Now, you're probably wondering, why are you writing about this common practice among youtubers and bloggers?
Well, I have been asked a couple of times to follow someone who has just followed me. I don't really know how to turn them down without sounding cocky or rude. How do you tell someone that that's just not how you do things?
Most of the time, I treat those requests with silence. Because some things are hard to say without having to explain yourself afterwards.