Board Thread:Lua Help/@comment-23880286-20150814202613/@comment-24473195-20150815093927

Vogel100 wrote: Abused how? The only way to obtain category lists is to query the database. While one or two queries are not a problem people can loop through a list and get categories for many pages. It isn't a problem for categories with few "members", but it is an issue if people obtain categories with thousands of pages.

They could add limits to how many pages are retrieved, or even increment the expensive counter. But it is still something that needs to be implemented carefully.