I received a (spam) email today from an SEO company.
Basically they did a quick review of one of my sites and one of the things they pointed out was that it was not good to have a hosted IP which is shared by 2 other domains.
I have several domains on my dedicated server. All three are clean, popular sites, although I have just launched a new site on the same server which is early days and still trying to gain organic traffic.
Can anyone confirm that hosting more than 1 site on a dedicated server can cause Google and other search engines to rank those sites unfavorably?
If you control all the domains that share the IP address, and if they are not cross-linking and trying to boost each other on the SERPs, then I don't think you have any problem with Google.
Troubles sometimes come when one domain shares an IP address with an independently owned domain that violates Google's guidelines. In the past that has sometimes created problems for the innocent domain. But even so, I haven't heard much about such troubles recently.
Some of my most highly productive sites are on servers with a single IP address and hundreds of other sites. Cross-linking on the same IP address seems to cause a problem though if it's done excessively, but in my experience it hasn't seemed to affect sites that have plenty of incoming links from other sources. What is more important is that the server is in your own country or that you use a country-specific TLD.
I would make sure you get yourself dedicated IPs for each site and NOT in the same "c" block. I, too, have a dedicated server with 5 sites on it, BUT I have assigned EACH site a unique, dedicated IP that are NOT in the same "c" class so I won't possibly run into those troubles with interlinking and all.