Many Postgres folks seem to think putting you rules in your database layer is a good idea, because you (1) get to deploy them automagically, (2) the commit logic is easier when there is no round trip, and (3) the PL/PGSQL language is actually pretty good.

I don't work on things big enough to think about this, and I would be curious if there were a summary of why/ why-not to put business logic in the DB, and where it SHOULD go.