[petercooper]

Back in ze old days, you could follow a ton of people, wait a while to see how many follow back (it used to be quite a lot), and then unfollow all the ones who didn't. Rinse and repeat and you get a lot of followers.

Eventually you'd unfollow a ton of people so that your follow/follower ratio looks healthier. For example, an account following 10000 people with 10000 followers doesn't look very authoritative. An account following 40 people with 10000 followers looks quite serious/valuable.

The reason this works is that people are notified of people who follow them but not of unfollows (they may have changed this but the fact is fewer people are notified of unfollows if at all).