In my eternal SEO reflexion, I came to ask myself the following question and would like your opinions: Do you think these factors would decrease your SERP or penalise you in Google presuming we have sites aboiut same topic and trying to rank for similar keywords ? - same Whois email for both url ? - same ip adress for both url ? - both url present and verify in Google webmaster tools ? - both url in same adsense account ? - both url in same google analytics account ? - can you think of another factor ? I hope my further SEO will confirm these but wanted your opinions and beliefs on the subject.
You are allowed to have two sites that are similar, and all the things that go with that (sharing whois/ip's etc).
But let say I have siteA and siteB all about cat food. Dont you think Google would have some kind of filter to avoid me dominating SERP for "Cat food" ? Would any of the criteria ask in original post be opart of that filter ?
Why would they? Google aren't interested in spreading the top ten spots between different people. They are interested in spreading the top ten spots between the most deserving sites. It doesn't matter who they're owned by. It's the quality of the material that matters.