This article is from the BiSexuality FAQ, by Jon Harley email@example.com with numerous contributions by others.
Posting to two or more newsgroups runs a greatly increased risk of starting
flame wars. It is not a good idea to start a thread between two newsgroups, or
even to follow-up to an existing cross-posted thread, unless you are familiar
with both newsgroups and the people involved. If you say something ignorant or
offensive, the resulting flames have a wider, more diverse audience, and tend
to grow exponentially.
A possible exception is posting announcements of general interest to two or
more groups. In this case we recommend including the header: "Followup-To:
poster" to indicate that comments should be sent to you via e-mail.
Be careful to look at and edit your headers so you don't unintentionally
spread cross-posts while commenting on other people's messages.