Limited profile patrons also allows quick sign up to any number of mail lists by providing only name and email info (rather than the usual new sign up or sign in process).
Quick Add Setup
And this is the same page opened in a script editor:

If the patron was not logged in when they subscribed to a mail list (the only gave their name and email), they will receive an email asking them to confirm their subscription to the mail list. Patrons who follow the usual sign-in routine will not be subject to this confirmation process.
If they do not confirm their subscription to the mail list(s), they will automatically be removed from the mail list after a specified number of hours (default 24) in Company Preferences. This occurs during the end of day process when other web information is purged.

If the email address a patron uses here exists in the database already, the patron in the database will be added to the mail list. If the email address does not exist, then a new 'limited profile patron' record will be created for the patron.