Some people seem to think that google and other search engines can be fooled into thinking sites owned by the same person are not really owned "by the same person" if the person has all of their sites spread out on multiple different IP addresses.

In the most basic example, if you have a site on 111.111.111.111 and it links to a site on 222.222.222.222 that google will rank each site higher than if both sites were on 111.111.111.111

Maybe this is true these days, i have not paid attention to search engine optimization lately, but when the rumor was circling the Internet when I came across it about 3 years back, I emails google support and they told me that there is no reason to rank a site lower if they share the same IP address.

My summarized answer (as I recall it) that I received was, that they understand that there are far more sites on the Internet than available IP addresses, and because of the fact that many sites have to share the same IP address, there is no reason for a penalization for sites that happen to share an IP address.

Perhaps this has changed but I doubt it. There are even less IPs available and even more sites on the web than there where when I asked them many years back.