Facebook is emerging as an important part of SEO. But, it is just a part of SEO. There are many other thing that needs to be done to promote the business online. You may promote your business on Facebook, but without a website it becomes difficult. People would want to know more about you and your business and that is not possible on Facebook. That is possible only through a website. You wont have to tell everything about you business on the Facebook or any other social media site. Just inform people about your website, and the rest will be done by your site.