Here are some sample letters:

Facebook exposure letters

Dear friend of Joe Scumbag,

It grieves me to write this letter but I believe all of his friends should know the kind of person he really is. Joe had an affair with my wife, Sally, from Aug until September. I believe that his friends should know this, so you can protect your marriage from him. My wife and I have 2 small daughters and this affair has almost wrecked our marriage.

I would be happy to provide the evidence to anyone who asks.

I would appreciate it if someone would notify his parents and ask them to call me at xxx-www-xxxx.

Thank you, BH

Dear friend of Skankyhola,

It grieves me to write this letter but I believe all of her friends should be aware that Skanky is having an affair with my husband, Joe. We have been married for 5 years. They have been having this affair since October according to the evidence.
I would be happy to provide the evidence to anyone who asks.

I would ask that you use your influence with Skanky to persuade her to leave my husband alone. You should also watch your own husbands around her because she is no friend to marriage.

I would appreciate it if someone would notify her parents and ask them to call me at xxx-www-xxxx.
Thank you, BW