I keep reading that you should put sites on different class c IP addresses if you want to do any cross linking. However, if the whois registrant is the same, is there any point in doing this? I mean, won't the search engines just think "same registrant / same owner" and so devalue the backlinks anyway????
If you are using private whois on every site anyway it won't make a difference. I'm not even sure Google takes whois info into account in its algorithm.
As a registrar, Google certainly has access to whois, and their algorithm patent specifically mentions using whois to determine common ownership. Aaron Wall believes they may factor in other types of data - such as all sites linking having the same registrar, all have private whois, etc. I would certainly use privacy if I wanted to try and make google think the sites don't share common ownership. Google stores vasts amount of information - so that brings up the question of whether or not that keep historical whois data and whether adding privacy AFTER would work and there really isn't anyway to know.
Can anyone explain what happens if you use WHOIS protection service, please? In that case Google's bot won't be able to determine common ownership right?
Privacy Protection hides your contact information, so if you buy it when you first register/transfer the domain into your name, they would not be able to see who actually owns it. If you add it after the domain has already been in your name, it's possible they could use historical data to determine common ownership. Unless the sites are hosted on different class c IP's, Google assumes common ownership regardless of the whois information. If you are running the same adsense account on both domains, then it would be pointless.
Nope. Even though Google may be a registrar themselves, they cannot get around Whois Privacy anymore than you or I can, unless as the poster above said - that they use historical whois data from before it had privacy enabled on it.