No World-Editing for anyone else, unless you're a part of the project. Meaning if you're not helping build the project, don't world-edit for anyone. For example, "Hey can you world-edit something for me really quick?" Say no.
Don't World-Edit in anyone elses property without permission. Don't move something that's not yours. This is abuse.
Keep in-mind you have a limit of how many blocks you can edit. If you care (I hope you do!) please don't world-edit so much in a short amount of time. - Honestly, placing blocks instead of worldediting until I know what I would like is better and faster.