I didn't need to wear a BS sign to let everyone know but I also did not hold back telling family or friends whom I wanted to be honest with and feel comfortable with. I needed them to understand that I was in pain, would not be myself and that I was not being a bitch to my FWH. I wanted to be congruent with my actions and feelings and not have to put on a front with others...especially family members. For me, this was a gift for being able to handle the stress of betrayal and to even try to focus on reconciliation.
Exposure is definitely an individual decision but many people who are told will not be too intrusive into the couple's marriage or overly resentful of a FWS. They have their own lives to focus on and will move on. I think the concern of exposure being a negative influence on reconciliation is sometimes over-inflated to protect the reputation of the FWS. However, I realize there are situations where telling certain people can truly be a detriment to reconciliation. If that happens though, those people can be cut out from interaction with the couple trying to reconcile.