Multi abuse
From A KoL Wiki
Multi abuse can be a problem, where a player has multiple accounts simply to farm meat and items for one central account. This is against the Policies of Loathing and may result in terminated accounts.
In the past, advertising budgets for Mall Stores were determined by a store's sales in a given week (which could be supplemented with explicit advertising meat payments). However, this became a standard multi abuse, where a player would use their multis to purchase from a store, and immediately send the purchased items back to the store-owning player. For this reason, Jick changed advertising to be explicit payment only.
Many of the hardcore and ronin rules were explicitly created to prevent multi abuse.