Placing the same content on a number of different domains doesn’t help you – it hurts you in the long run. Erik Dafforn recently covered the issue of domain mirroring in a recent ClickZ article titled Domain Mismanagement Plagues Search Performance. In many cases, companies know that this doesn’t provide much, if at all, improvement for search engine rankings… but what they don’t know is that domain mirroring can hurt them in the long run.
However, don’t start auctioning off all of your other domains just yet! The easy solution is to set up 301 redirects to your one central website for all of your domain mirrors.
Another domain mismanagement issue is canonicalization. Erik provides this solution:
“One of the two main canonical issues is “www” vs. no “www.” Simply put, only one of these versions of your site should be live, and the other should redirect (via 301) to it.”
Agreed. These two domain issues are essential building blocks for any SEO campaign & should be dealt with first before any content considerations / revisions.
So if I were to provide a last example of why having multiple domains is a bad idea, I guess I would say this: owning multiple domains & putting the same content on each one can be compared to a rock band releasing separate singles with different titles that sound pretty much the same (though Nickelback has demonstrated this…)- potential customers get confused & begin to develop a lack of trust.