[throwaway1979]

Specifically, a place where DBs use bloom filters is distributed joins. This isn't a common scenario IMHO. Found a good description here:

http://www.coolsnap.net/kevin/?p=19

P.S. Loved the tutorial.

[supergirl]

it's also useful on local hash joins because it's faster than a regular hash table lookup. so you can use it to eliminate some stuff before going to the big hash table.