SharePoint's Members-Only Security Model a Flaw

SharePoint is a collaboration tool, but its default "private" security model really gets in the way of that. At least that's how it is set up where I work. Time and again, somebody will take time do do the right thing--post meeting notes in SharePoint, and email the link only to the meeting attendees, rather than just blasting out a quick email, for instance--only to receive a cascade of replies saying "I can't get in to the site".

I know, there is probably a setting in SharePoint administration not do that, but it's a bit like systems security—however it is set out-of-box is what matters, not how it can be set if you have the mental model and motivation to do so.