Google Knows All About the Domains you Own

At the recent WebMasterWorld Pub Con get together, Matt Cutts (who is basically Google's link to the search engine world) reviewed some sites as part of a panel.

Cutts very quickly and easily ascertained that the owner of site A also owned sites B, C, D, E, F, G, etc. even though, apparently, many of these sites were registered using the Private Registration feature registrars offer.

While owning web sites that link together shouldn't be enough to devalue the links between sites -- the ranking should be about the quality of those sites -- I can't help but wonder if there wouldn't be an automatic red flag alerting Google of the relationship.

The lesson: if you're optimizing your site for search engines, the links from the other sites you own may not be as valuable as you think. At the very least, Google knows you own these other sites, and knows of the relationships between them.