A lot of times, webmasters will buy multiple domains to take advantage of the possible variations of their specific keywords. This is fine as long as in doing so, the correct methodology is implemented. If I buy domain A and create content for it and then buy domain B and use the same content, I now have what is considered to be “duplicate content”. This is not to say that Google or Bing will necessarily penalize anyone for doing this, but there will certainly be ranking ramifications if your domain configurations are not set up optimally.
For instance, Google may decide to index content from one site, content from the other site and combine the results in the results pages. Link value tends to get split between all the different incarnations of your content and the site becomes less of an authority; completely diminishing all of your SEO efforts.
When it comes to duplicate content, most webmasters don’t realize the negative ramifications from it. There will usually not be any kind of “penalty” or “punishment” imposed by Google, but there will be the reduced effectiveness for their primary keyphrases.
How does one tackle the problem of duplicate content? The first option should always be to avoid having duplicate websites in the first place, but the main ways to remedy the situation are either; 301 permanent redirects from the duplicate domain to the preferred domain and the second (and probably the tougher) would be to just have two distinct websites with completely different content and goals. One website could be for your consumers and the other could speak to/sell to your business clients.