You only "friend" people in real life who you trust not to act maliciously. If you unwisely trust someone who is malicious, you encounter various problems, just like in real life. But it would be very difficult for a malicious person to construct a realistic-looking subnet of sockpuppets because that would require getting lots of real people to make that unwise decision.

Not saying this is perfect, but I predict that the vast majority of users who "friend" 20+ people irl who also have friends will be fine, and borderline cases will be borderline.