When outlining the use of team branches on Launchpad previously, I used the --create-prefix option when pushing the branch to sftp://bazaar.launchpad.net. This was to make sure the initial push would succeed, even if the /~username/product directory the branch would be created in didn’t exist.
To simplify things for users, we made a change to the SFTP server in the latest release, so that --create-prefix is no longer necessary. This does not affect the allowed branch directories though: the structure is used to associate the branches with products, and decide who can write to the branches.
Another change included in the rollout is the ability to rename branches and reassign them to different owners through the web interface. So for instance, you can give ownership of a personal branch to a team your project grows to multiple developers. This should be used sparingly, since it will change the published branch URLs which can confuse people using your branch.