I don't think it's necessarily about perfection on release (though certainly sometimes it appears that things were never user tested).

Reading through Scott's article, he points out that it's not uncommon for an issue to be raised by many users and ignored by the product owner (my personal pet issue at the moment is Google Calendar no longer allowing me to accept invites sent to non-GMail addresses).

It might not be cost-practical to fix issues that affect a small section of your audience, but I'd like to think there's a certain qualitative aspect that comes into play, and if the issue affects 'n' people it should get a banner regardless of whether 'n' is only a minute percentage of your audience.