indices are a standard feature in databases, and yes, they can slow down some queries while speeding up others, so you should use them judiciously. maybe BFS has an issue there, but that does not negate the concept.
practically speaking, what i want is a gui filemanager that lets me set arbitrary keys and values on files, display them and filter for them. indexing them is not required.
btw: UK style power sockets all have individual switches to turn them off or on. maybe elsewhere people aren't bothered because they are not used to the idea.