In the last couple days, two unrelated patches were committed to Drupal 6 with a common flaw: they caused inconsistencies between the database schema as defined by every module's hook_schema() function and the actual layout of the database. They are not the first two; I've personally found and fixed at least a dozen such mistakes, usually via a follow-up patch after the bug has already been committed to CVS. What makes these bugs so irritating is that they are so absolutely trivial to detect and usually very easy to fix before the initial patch goes in. Fixing them afterward takes a lot more overhead (and, more importantly from my narrow point of view, my overhead). So I want to put an end to it.
Therefore, with no authority whatsoever, I hereby declare the following law:
Every developer that submits or reviews any patch that modifies a Drupal 6 (or later) .install file must install schema.module and, using its Compare report, assert upon pain of public humiliation that the patch introduces no database schema inconsistencies into a fresh install or an upgrade from the previous core version.