It isn’t uncommon for webmasters or SEOs who operate numerous sites in a network to ask how many of them they can link together without bringing down the ax of Google. Finally that question made its way to Google’s head of Webspam who responded in one of his regular YouTube videos.
The question was phrased “should a customer with twenty domain names link it all together or not?” While blog networks can easily find legitimate reasons to link together twenty or more sites (though Cutts advises against it), it seems interesting to use the number in question to discuss normal webpages. As Cutts put it, “first off, why do you have 20 domain names? […] If it is all, you know, cheap-online-casinos or medical-malpractice-in-ohio, or that sort of stuff… having twenty domain names can look pretty spammy.”
When I think of networks with numerous full sites within them, I think of Gawker or Vice, two online news sources who spread their news out across multiple sites that are more focused on unique topics. For example, Vice also runs Motherboard, a tech focused website, as well as Noisey, a site devoted to music. Gawker on the other hand runs Deadspin, Gizmodo, iO9, Kotaku, and Jezebel, among a couple others. Note, at most those networks run 8 unique sites. There is little reason any network of unique but connected sites with more parts than that.
However, there are times when having up to twenty distinct domain names could make sense without being spammy. Cutts points out that when you have many different domain names that are all localized versions of your site, it is ok to be linking to them. Even in that scenario however, you shouldn’t be linking them in the footer. The suggested fix is to place them in a drop down menu where users have access.