I feel like a lot of people are seeing "follow recommendations" and freaking out, so two thoughts:
1) There's no magic algorithm present. Follow recommendations are literally "hey, you boost and favorite this person's toots a lot but aren't following them". It /can't/ recommend someone you're not already interacting with.
2) It's part of the server API, not the user interface. If it hadn't been in the patch notes you'd never know it was there.