Multiple domains the world of online commerce is still relatively young and as a result there were various techniques which allowed people to gain an unfair edge when it comes to search engine rankings. Fortunately though, search engines evolved their algorithm over time to help counteract dubious techniques. However, even to this day many people still believe that creating domains for the same service is going to bring them better traffic. Let me put it there bluntly: unless you do it in a certain way this method is everything but advantageous, especially from an SEO standpoint.
why these domains are mostly bad for SEO is the fact that you are going to be having duplicate content all over the place. Search engines generally dislike duplicate content and as a result all websites except the one with the original content tend to lose their search engine rankings after a little bit of time. If you want to avoid the duplicate content problem you are going to have to write unique articles for every one of your websites, meaning you will have to dedicate a lot of time and resources into managing all your websites.
The second problem you are going to have from an SEO perspective is the fact that your websites are going to be competing one against the other. Instead of increasing your chances of attracting more visitors it will drastically decrease your chances of ever gaining profits from all but one of those websites.
Seeing as how your duplicate domains are going to be rendered obsolete you will also be wasting money; don’t forget that hosting usually costs $12 per year, which is money that could otherwise be spent on further promoting your service, which as you can guess would bring you much better results.
In addition to that, customers these days are quite suspicious of scammers and the majority think they are dealing with one when they bump into the exact same business on different websites. In this business, your reputation is everything and if you are known as being a dishonest scammer who wants to use shallow techniques to get people to visit his website, chances are you will have a very hard time making a living.
On top of everything, if you have multiple websites it also means that the number of backlinks to each domain will increase. While at first it may sound good, it actually isn’t seeing as how these backlinks are going to be spread across a multitude of websites, which in turn means that their benefits are far inferior to what you would get if you had them all point to your main website.
However, there is always some type of exception to the rule and in this case it is when you are looking to open up country-specific domains to bring your business abroad seeing as how they will rank on local search engines.
At this point you can hopefully see why multiple domains are mostly bad for SEO and that it is far better to concentrate your efforts on marketing one site rather than spread your efforts thinly through cheap duplicate copies.