Under present norms, if Alice associates with Bob, and Bob is considered objectionable in some way, Alice can be blamed for her association, even if there is no sign she was complicit in Bob’s sin.

An interesting upshot is that as soon as you become visibly involved with someone, you are slightly invested in their social standing—when their social stock price rises and falls, yours also wavers.

And if you are automatically bought into every person you notably interact with, this changes your payoffs. You have reason to forward the social success of those you see, and to suppress their public scrutiny.

And so the social world is flooded with mild pressure toward collusion at the expense of the public. By the time I’m near enough to Bob’s side to see his sins, I am a shareholder in their not being mentioned.

And so the people best positioned for calling out vice are auto-bought into it on the way there. Even though the very point of this practice of guilt-by-association seems to be to empower the calling-out of vice—raining punishment on not just the offender but those who wouldn’t shun them. This might be overall worth it (including for reasons not mentioned in this simple model), but it seems worth noticing this countervailing effect.

Prediction: If consortment was less endorsement—if it were commonplace to spend time with your enemies—then it would be more commonplace to publicly report small wrongs.