nomis5 - 6:47 pm on Oct 24, 2011 (gmt 0)
There's no way that whois privacy will keep anything private. To believe that is just hiding behind a see through plastic screen.
As far as it being a ranking factor then I don't see what impact it could have other than Tedster's observations.
If I have two or more related sites then I link (not over-link) between them. I think Google would expect that and not penalise it.