I’ve noticed that one of my competitors has created multiple copies of their website under different domain names. Isn’t this spamming, and is there anything I can do about it?
Yes indeed, this is considered a form of spamming.
If you discover this form of misbehaviour as a result of a search engine results page, you should report the result to the search engine. On Google, for example, you should Report a Spam Result and give details of the search you did and the results you were unhappy with. When reporting spam of this type, stick to the facts without mentioning how and why you feel so upset. There’s no point in telling Google that you feel your site is so much better than the spam site, or that you think their web designer must be colour blind. It could well be true, but it’s irrelevant.
You should use the same spam report form to report anything you feel Google should be aware of, if you suspect they are not.