Is there a way to configure all profiles to default to having both the Profile Visibility and Contact Details options checked by default.

Allowing people to opt-in is much better than opt-out in my book. Keeps the newbies from doing something they do not understand that may be bad.

I concur. I added an Email address field to the profile so that classmates can share their email address with everyone subscribed to the site. I am having to check the "Profile Visibilty" box when newbies join the site and fill in this field so anyone on the outside can't see their email address.

I dunno -- I'm kind of on the fence here. 45% of Classmates choose to leave their Profiles public so they can share them with friends, family members, etc. And I'm more on the fence about preselecting the option to share a Classmate's email address with fellow Classmates. I consider clicking on that box to share it to be an act of opting in. If we preselected it and people had to uncheck the box, I'd consider that to be an act of opting out. Or so it seems to me.