Quoting from the blog post:
Until now, if you wanted to use FamilySearch.org on behalf of someone else, you had to know the contact name and helper ID of the person being helped. This required that person being helped to have an LDS or FamilySearch Account, which was sometimes very inconvenient. In many cases. Not many users are able to actually remember their contact names.
You can sign in as a helper from Family Tree, the Temple List, the landing page for the My Family: Stories That Bring Us Together booklet, and from the Photos section of FamilySearch. (This ability in Photos is new and discussed below.)
The latest improvements now allow you to:
Sign in to help someone, even if they don’t already have an LDS or FamilySearch account.
Use either of two sets of information about the person you are helping. The first default screen asks for the person’s user name and helper number. Being able to use the username is a change. FamilySearch used to ask for the contact name of the person being helped.Here is a screenshot of the form for Helping Others using their Username:
Here is another screenshot of the form for using the person's Full Name:
This should be a very useful change and eliminate some of the problems associated with helping people with the Family Tree program.