I was attempting to export an IIS 6 website using the Web Deploy Command tool when I ran into an error:

Error: The property 'value' located at '/metaKey[@path='/lm/w3svc/12130']/metaKey[@path='ROOT']/metaProperty' is marked as secure. You must specify an encryption password to archive this property. Error count: 1.

It appears that you have to specify a password to create the archive, with that, I added the following to my command:

msdeploy.exe -verb:sync -source:metakey=lm/w3svc/12130 -dest:archivedir=c:\archive,encryptPassword=[pass] > wdeployarchive.log

Problem solved!