OpenForce implemented something similar to this for
GreenOrder, although not quite what you're talking about.
However, what you're talking about is pretty easy to do. You can
have a scheduled proc that checks for users who fit your "this
guy now needs to verify his email address" check (days since
registration, etc...), and updates the user_state to
needs_email_verification. OpenACS 3.2.5 will gracefully handle
this the next time the person logs in. The one thing I'm not *
certain* about is exactly what happens if the user is permanently
logged in... you might have to hack something there.