For all of these tasks below, it is assumed that you are logged on and have navigated to the User Accounts page (Admin/User Accounts).

A) To force the user to enter profile information at registration, do the following:

1. Click the "User Settings" link
2. Under the User Accounts Setting, set the "Require a valid profile for Registration" to be checked on
3. Click "Update"

B) To set a default value for a registration field, do the following:
    The following steps "appear" to be the way to do it, but I haven't seen it work yet on my local install of DNN 4.3.2. I haven't done thorough testing yet, but by all appearances, this seems to be the intended way for it to work...

1. Click the "Manage Profile Properties" link
2. Click the edit pencil for the property you want to set a default for, and enter the valud in Default Value
3. Click "Update"

On the last point, I'm not sure what you are referring to. The only users who should be able to choose the visibility of individual profile fields should be the Admin or Host.

On point B) After re-reading the post by Charles Nurse (see here), I see that the Default Value is not implemented yet.

On point C) (the aspect of users editing visibility of their details), I wonder if that is for what a user wants other users to see of themselves. That would make the profile properties act as information not just for Admins, but for other modules to leverage in showing info about a user (for example, a forum module that allows others to see info about someone who made a post to the forum) while allowing the user to determine the amount of self-disclosure they want to have.

I'm just guessing on this last point, of course, but it would sound like a good feature. Maybe a Core member familiar with the profiling could comment (e.g., Charles Nurse) on the accuracy of my speculations...