I use a facebook page as part of my branding and marketing program. There are a lot of moving parts on the social media end of branding and marketing and facebook can be an important element. I also use twitter, pinterest and I have plans to add google+.
The goal is not just direct sales but keeping an open and friendly channel of communication open with my customers. I definitely get sales through social media outlets but it also helps with credibility. People feel like they have access to the people who have designed the products and actually make them so we don't come off as some random company seeling stuff we bought in China and marked up.
It is also great for getting feedback from customers and people who may not have purchaces but are still interested in what we have going on.
In addition, being active online helps with search engine optimisation. The better we do at that, the more people can find us through google searches.
It is always a work in progress but if you can and want to put some time and consistancy into it, you can get good results.
Lucia~
http://www.luckydogleather.com