I called this one back in February!
http://www.vmwareinfo.com/2009/02/duplicate-sids-big-deal-why-you-might.html and Aaron Silber sent me over this note to confirm it! :)
Looks like our old friend has been put to bed.
A very good read, the bottom line is he says that after much investigating the local machine SID is exactly that, just local and is never used outside the machine, so there is no reason whatsoever to have them be unique; there is no chance that any machine could ever find out what another machine’s SID is.
Here is the final nail in the coffin, he says:
“To my chagrin, NewSID has never really done anything useful and there’s no reason to miss it now that it’s retired. Microsoft’s official policy on SID duplication will also now change and look for Sysprep to be updated in the future to skip SID generation.”