different IPs are very important. well.. according to the google patent article that i read. it appears they check for same ips, same IP blocks, DNS registration information such as date of registration , how long they are registered for as well as DNS server information.
pretty crazy those google guys.
here's someone's take on the google thingy.. you guys have probably already read something similiar to this.
http://www.mediajunk.com/public/archives/000365.html