Multiple Domain Names & SEO

When performing searches; highly placed sites often include all or part of the search term(s) in the Domain.  So what exactly does this imply?  Does this mean that procuring several or more domains including your desired search terms and pointing them to your site will improve your search placement?  In fact, only one domain, the primary domain carries search value from a search engine algorithm point of view. Search engines do not want to give sites preferential ranking simply because someone purchased and pointed additional domains to them. Indeed, if one improperly sets up multiple domains to appear to be live for the same site, today's algorithms will detect this as a "black hat" SEO practice and very likely result in blacklisting or severe downgrading of the site for search placement. 

Multiple Domain Names do have value for brand protection and for marketing campaigns and can be very strategically valuable for these reasons.

Multiple Domains do not help with SEO. However, it is true that important key phrases or terms in your domain can be a benefit to your placement for those searches and therefore, it may be worthwhile to consider using a search oriented domain if that is very high on your priority list. In that case, changing your primary domain can be a benefit to your SEO.