Why? Is this one of those "The Mall Is The Game" things?
If I am on a store's forbidden list then mafia already hides the store from me, correct?
If the store is on my forbidden list I suppose this could be useful but unless there is some kind of personal vendetta I don't see any use for my forbidden list.
Usually when I ask questions I am not convinced something is useful or necessary or of general interest. In this case I'm really asking about the motivation for having and using forbidden lists. Given that they are a thing, I don't see a problem with doing this.
In this case the general use is to avoid buying from stores for various reasons.
Such as for an example, a store that caters to newbies but you like buying that item. Or you have a mall bot that you don't want to buy from.
My specific example is a multi I control for some functions with chat, such as running a specific script or diagnostics.
So I don't want to ignore that. But I accidentally used it to buy from my main store because I was in the relay page and didn't notice and just wanted to be clever and unstock my store by buying the items instead of using the store manager. AKA, multi abuse.
It was originally added for duffo, used by people that didn't want to hurt the project by buying items that were limited to one a day. Those items were mall min and the store owner had issues with people making multis to buy the items.
So adding to forbidden stores meant we didn't accidentally buy that item.
Also it means you can choose not to buy from the store of someone who's practices you dislike, such as buying everyone out just to raise the price artificially.