According to The Web Application Graveyard, created in 2015 by ale,
questions on applications or application features that are no longer available are off-topic for Web Applications as no one will ever be able to make use of the answers again.
then
Such questions should be Closed with the community-specific reason. Use Other - add a comment
So my "plan" is when a question appears on the Homepage or on the Related questions, look if the question includes one of the tags of the known defuncted web applications.
I put plan between quotes because there is no due date or specific time assigned to work on this. Consider this as a piece of paper in a task jar.
If someone is interested in joining, please add a comment.