Despite the man entry, it looks like -B 'none' does not work with lxc-create 1.0.0.alpha1. You'll get an error as follows:

    lxc-create -B 'none'  -t ubuntu -n foo
    lxc-create: Failed to create backing store type none
    lxc-create: Error creating backing store type none for foo
    lxc-create: Error creating container foo

Probably better to use 'dir' here, or don't base the -B option at all in lxc-create if backing_store is undefined