Potential spam on a story usually means there's a suspicion that the content might be unwanted or excessive and could be considered as junk or irrelevant.
The term 'spam great big story' is rather ambiguous. It could be a made - up or very specific term within a certain community. If we break it down, spam is the unwanted stuff. 'Great big' implies something large or significant. So it could be about a really big or impactful spam situation. For example, it might be a story about a spam wave that flooded a particular network or platform, causing chaos and disruption. Maybe it involved a new type of spam technique that was hard to counter, and the story would detail the efforts to deal with it.
One sign is that they have no profile picture or very generic pictures. Another sign could be that they follow a large number of accounts randomly but have very few followers themselves.