We've tried to keep a cap on that. However, we need to learn how to add metadata to the brain.
For example, our site adds video and audio icons to story listings if the story contains a video or audio.
Unfortunately, to find out if a story has an audio or video can become an expensive call that requires a getObject()
So, any story listing that used to be brain driven now is object driven. (kept in check by a limit of no more than 10 or so objects)
But, what I'd like to do, is create bool metadata on this, and have it returned in the brains.
The project got back burnered. Mostly because the performance lift from such work is not worth it, and would require a reindex once completed - which pisses off sysadmin.