When generating a new mean application using the mean-cli generator available from http://mean.io you may get the following error:
EACCES, mkdir '/Users/darren/tmp/npm-NNNNNNNN
Where NNNNNNNN is a random alpha numeric.
This is caused by the tmp folder being owned by root when it should be owned by the user (darren). To fix this execute the following in the terminal.
sudo chown -R `whoami` ~/tmp