I ran into a situation where I created a User Profile Property with the Replicable checkbox set, which had a really long name. There were no errors when saving the profile property, however later on I started receiving errors in the Event Log:

failure trying to synch site [guid] for ContentDB [guid] WebApp [guid].  Exception message was A WSS internal name for profile property ‘ProfilePropertyWithReallyLongName’ could not be found..

Apparently SharePoint has a limit of 32 characters for Internal Field Names. This will also apply to Replicable User Profile Properties since they will get synced down to the WSS Content DB in the UserInfo list.