Static IP vs. Shared IP

This may explain why sites with addon domain names rank so poorly in Google:

Google in particular and possibly other engines look at these static and shared IP. As I was explained when I search engine spider first comes across your site it will parse it with basic HTML 1.0. If its able to do this then it will normally go about getting spidered and indexed. For those sites with a static IP address they will get spidered with HTML 1.0 as its able to resolve the address immediately. If by chance you don’t have a static IP address, Google may go about parse the site with HTML 2,3,4 and soon until its able to resolve the address for your specific site. This can take up to 3 months to happen. In the meantime it will use the IP of the main site on this IP, often times the hosts site. It will come back until its able to find your specific IP. During this period of 1-3 months, any links that you build to your site that is found by Google, will get credited NOT to your site, but to the main root site on the shared IP, often times your host site.

Read the whole post titled “Why Using A Static IP Address is Benefical… Google Engineer Explains“.