Natasha Lomas, writing for TechCrunch:

Two WhatsApp blog sites, and WABetaInfo, report spotting notification messages in the app which appear intended to warns users that they are at risk of forwarding some spam — by displaying a notice that the message “has been forwarded many times”.

A similar warning is also shown displayed on a frequently forwarded message when it’s received, although the feature is described as still in development and it’s not clear whether WhatsApp intends to officially roll it out or not.

I think WhatsApp first needs to offer a way to mark messages manually before they introduce the feature described above.