The problem with companies that specialize only in getting good search engine rankings, is that what they do can be bad for your overall marketing.
We see instances of this daily. For example, home pages loaded up with menu items that overwhelm and confuse visitors to the site. What good is it generating traffic to your site if they all immediately leave?
Another trick is to use a URL that contains keywords but mobs you up with a bunch of other companies to a point where you all look the same.
The problem of course is most SEOs (Search Engine Optimization companies) are not marketers. They are technicians who know something about how Google works.
Any effort to get high search engine rankings should really be part of, and integrated with, a complete marketing program.