Google webmaster guidelines > Technical guidelines > Guideline five of five in this category states...
"If your company buys a content management system, make sure that the system can export your content so that search engine spiders can crawl your site."
Definitions-
content management service - Also referred to as a CMS, content management systems allow information to be published to a website without knowing HTML. They are also used to more effectively allow several users (employees for example) to add information to a website. The CMS updates a database and then the website retrieves information from the database. This creates dynamic web pages.
search engine spider - Also known as a "bot" or a "crawler", a search engine spider follows links to web pages and then reads and retains the information it finds. This information eventually becomes the "copy" of a website in a search engine index. This process is often referred to as "crawling" the web. "Googlebot" is the name of the search engine crawler that is most used by Google.
Examples and Explanations
Content Management Systems must create pages that are understood by search engine crawlers in order for your website to be properly indexed by search engines.
There are many different things to consider when choosing a content management system (CMS), but this guideline only states one. To follow this guideline your CMS must create web pages that search engine spiders can crawl.
Every content management system in some way takes your data and turns it into web pages.

The web pages that come out of the content management system should be able to be understood by Googlebot.
If you want your website to follow the Google webmaster guidelines, your CMS must have the capacity to create search engine friendly pages.
As a very simple example of this, the Google webmaster guidelines state that "not every search engine spider crawls dynamic pages as well as static pages". If you want to follow that guideline it would make sense to have a CMS that can provide static pages.
It might help to think of a content management system the same way you think of a webmaster.
Would you hire a webmaster who could not create web pages that follow the guidelines? When deciding on a content management system make sure it can do what you need it to do. If following these guidelines is what you want, then find a CMS that results in pages that follow them.
Resources
An informative article on CMS:
Choosing a CMS to build your website
Content management systems defined by Wikipedia: