We're converting all SP permissions into ActiveDirectory groups (one per uninherited object, per role level). I wanted the group names to reflect where the permissions were/are, so I assigned each group with a name that matched the site structure:
sitecollection|site|list|Full Control
Active Directory had issues with the pipes and the potential length, so I reconfigured everything to use the description of the Active Directory object instead. The actual CN of the group is -someNumber-
(-1-,-2-, etc).
I ran across an interesting phenomena while adding the groups into SharePoint under the same role level; I had to start the groups at 1000 else the EnsureUser couldn't find the group no matter what.
$web.EnsureUser('c:0-.f|myprovider|-1-')
says it doesn't exist, whereas $web.EnsureUser('c:0-.f|myprovider|-1000-')
does just fine.
Is there some sort of limitation to the number of characters a SAM Account Name / Principal Name must be when being searched by SharePoint?