Originally Posted by mdw
Google doesn't care how many are mapped to a single IP, it only notices when sites on domains hosted on the same IP address have links to each other. That link may be a bit less valuable than links to another IP address. A collection of sites that are on the same server and have links to each other is something their algorithm looks for I think.
But I do it en masse anyway, and have gotten sites with good PR in spite of it so perhaps it's not very important to them? That would make sense because many commercial hosts have thousands of domains per IP all belonging to individual customers.
I read somewhere google checks whois when deciding pr value?