OK, since postfix was mentioned earlier as aservice which would need this (binding to interfaces): changing the postfix config from "listen only on localhost" (similar to what sendmail does in it's default config) to "listen on an external network interface" would change it's dependency: in the first case it does not care about external networks (localhost is always available), in the second case it does.
How is this supposed to be managed?
This is going to be true of a lot of system services that pre-date the hot-plug paradigm and don't respond dynamically to changing prerequisites. BIND has the same issue. My guess is that until those services become hot-plug-aware, they'll have to be restarted with different configurations for each possible environment. That's yet another reason a clean generic solution isn't possible to retrofit non-intrusively.
