The crowd shares the fun. Consequences get handed out one name at a time.

Afterwards, nobody is dealt with as a group. Twenty people were there and the letter, the suspension or the fine goes to whoever can be identified, which is frequently not the person who started it. The ones who suggested it are often the hardest to pin down.

If something is going on and you would not want your name read out next to it, that is your answer. Leaving is not the same as telling on anybody. Being the person who was not there is a perfectly good position to hold.