WebProNews has this highly informative article about the topic of whether one should perform SEO work inhouse, or outsource it to the experts.
Among one of the compelling reasons for outsourcing that was not discussed was the concept of TIME. How long before your inhouse can produce results? The veteran SEO can probably do this faster. While the newbie in house techie, would need time to familiarize with the steps involved.
However, one reason companies prefer to keep their SEO inhouse is to keep its trade secrets and web marketing statistics to itself. For this, companies often take a middle ground – that of hiring SEO experts to train inhouse staff to do the SEO work for themselves.