IMHO we should list spam should be performed on a global basis. It's not uncommon to receive on Foo-owner-l an email with To: header pointing to bar-l Assuming that on foundation-l they don't need bigger penis more than the stewards or wikibots, if a message is discarded (or marked with a new type spam) on 3 such lists, something like on all on which it may be present (a notification delay may be appropiate). Add rules complexity at will.
Also, mailman default email addresses are too machine readable.