Hi there, Elliott with the Data Work Group here. Arch is right about the tag for abandoned trails but it AllTrails is also rolling out new tools to help users better understand what is private property based on tagging. 

It also appears there is a bit of an edit war with some suss reverts in recent days around this trail. Are we all clear on what it is/isn't?

Thanks,  
Elliott Plack  
OSMF Data Working Group