I have about 15 websites all linked to each other and they all show me as the owner in WhoIs. I also link to a few of my friends blogs from all 15 sites.

Does anyone truly know how important site ownership is with regards to the value of links from those 15 sites? They have decent PR and link profiles, but is it all negated by common ownership?

Does having one owner of all these domains hurt my link value to other sites? Would it help if I made them all "private"? Or to get the max benefit, do I really need to go into GoDaddy and set up 15 different "owners"?

When you interlink 15 sites the search engines (only one of which I believe, Google, is a registrar), don't have to look at whois data -- you've already told them the sites are related by virtue of the interlinking. ;-)

If everything is going well and, as you say, the individual sites have decent link profiles, I wouldn't worry about anything. In cases like this I usually use the example of big packaged goods companies that interlink different brand sites: if it's open, above board and not meant to deceive, then it's fine.

also are you hosting them all on the same server

also are you hosting them all on the same server

They are all hosted at GoDaddy and came online at different times, but some might be on the same shared server. All have unique IPs -- not necessarily class C, but all unique IPs.

If they are the same c class they are seen as connected and will further lessen the link impact