Sure:
Using phabricator with a various team on different project not every need to see the task I am adding to phabricator.
When I do arc todo "some task" the task is visible to all user by default. This is a problem for us as a lot of users on our platform are external contractor and don't necessary need to see what is happening in other projects.
I was thinking something like arc todo -u "me" "some task" or arc todo "my task" --private so that only the creator of the task will be able to see the task in phabricator

I read all this thread and still cannot figure out if I can apply any policy or privacy setting for a project. It is a real trouble. Projects need documentation. But not everyone should access this project.
How does Phabricator approach this issue?

agree - I am confused between our own install and the main phabricator and need to check URL often...