As a general rule, it is important that users log in when making changes, because the changes can then be attributed to their username. You'll find that regular contributors are generally more suspicious and more critical of edits that are made anonymously. But more than just assigning credit, logging in is important so that others can contact you if they have concerns, questions, or compliments concerning an article you wrote. Logging in helps to build the team, and helps others come to trust your contributions.