This is very interesting. Devlin Daley is in the last phases of building a bloom filter for CouchDB. Taking advantage of various reusable components available out there in the Vast Internet, he uses map to set up a bloom filter for a given element of a given document, and the reduce to combine all of these into a single bloom filter. Et voila!
Once this is done, definitely something to keep in the toolbox. Thanks, Devlin!