Destination directory is not writable (OSX)

brian at rl: ~                                                                                                                                        ▸▸▸▸▸▸▸▸▹▹
→ drush dl aegir-up
Project aegir-up (7.x-2.0-alpha1) downloaded to /Users/brian/.drush/aegir-up.                                                                        [success]
Project aegir-up contains 0 modules: .
brian at rl: ~                                                                                                                                        ▸▸▸▸▸▸▸▸▹▹
→ sudo drush dl drush-vagrant drush-hosts
Password:
Project drush-vagrant (7.x-2.0-beta5) downloaded to /Users/brian/.drush/drush-vagrant.                                                               [success]
Project drush-vagrant contains 0 modules: .
Project drush-hosts (7.x-1.1) downloaded to /Users/brian/.drush/drush-hosts.                                                                         [success]
Project drush-hosts contains 0 modules: .
brian at rl: ~                                                                                                                                        ▸▸▸▸▸▸▸▸▹▹
→ drush vagrant-build --blueprint=aegir
This appears to be your first time running Drush Vagrant or your user settings (~/.drushrc.php) have been deleted.
Drush Vagrant Integration requires those settings in order to function properly.
Proceed? (y/n): y
The following settings will be added to your ~/.drushrc.php:
  username .............. brian
  user id ............... 501
  group id .............. 20
  Git username .......... Brian Gilbert
  Git email ............. brian@mydomain.com
  User's home directory . /Users/brian
  Projects directory .... /Users/brian/vagrant/projects
  public(ssh_keys) ...... /Users/brian/.ssh/id_rsa.pub
  private(ssh_keys) ..... /Users/brian/.ssh/id_rsa
Are these settings correct? (y/n): y
The directory you specified for your projects (/Users/brian/vagrant/projects) does not appear to exist. Create it now?: y
The name of your project may be used in URLs, and so should only contain lower-case letters and numbers.
It may also contain hyphens (-) and dots (.), so long as they do not come at the beginning or end of the name.
What would you like to call your project?: aegirdev
Would you like to generate entries in /etc/hosts for the VMs in your project? (y/n): y
You are about to:
  * Create a new project called "aegirdev" at "/aegirdev".
  * Add entries for the FQDNs of the VMs to /etc/hosts. (You will be prompted for your sudo password.)
  * Generate Drush aliases for the project and VMs.
  * Launch the project VMs immediately.
  * Build the project using the "aegir" blueprint from the "aegirup" extension.
Do you want to proceed with initializing the project? (y/n): y
Destination directory / is not writable.                                                                                                             [error]
The following errors occurred when running "drush_copy_dir()" in "vagrant_default_build_project_dir()".                                              [error]
Drush command terminated abnormally due to an unrecoverable error.                                                                                   [error]