While playing around with my Puppet configuration I discovered that the 'system facts' returned by the Facter helper tool were not consistent on my Debian boxes.
On some machines Facter properly reported all LSB related facts of the system, while on other machines it did not report any such information. The problem occurred on about 50% of the hosts, so I excluded a bug introduced by manual over-tuning of the system configuration.
Further investigation showed that Facter uses the lsb_release command to collect the LSB information of the system. On Debian this command is provided by the lsb-release package which was only installed on half of my systems...
Now my Puppet manifests include the following configuration directive which should prevent this problem in the future :-)