Facebook can be beneficial from an SEO perspective. The actual text within a Facebook Business Page's title is searchable not only by Facebook but also by Google and other search engines. The About box and thecontent within each post are also crawled by the search engines. Consider the screenshot below.
Every time you post a Facebook status update that includes a link to content on your website - it's seen as another reputable link back to your site. This aids in the optimization of your website, in addition to the SEO opportunities of the Facebook Page itself.
In some cases, Facebook Pages show up higher than their associated websites in search engine results for keywords related to your business.
Finally, if a website has the Facebook Like Box social plugin installed, when the plugin pulls in the latest two or three posts, that content is seen by the search engines as fresh content with keywords. This concept is very similar to when you post a new blog post. Check out the screenshot below for an example of the social plugin.