Yes, Social media is a way to promote your business, a way to post positive and feel good images and a way to remind people that you're there ready to provide them with what they need. But, it's also your new Customer Service Center.
I've seen too many businesses not reply to customers questions or replies on FB or Twitter too often. These social media outlets are your new customer service. Just like people stopped calling in favor of emailing about ten years ago. People now don't even email, they go straight to the FB page or Twitter and post a comment - and this comment is public! So, if the comment is not positive, everyone can see it - and they can also see when you don't reply.
Another reason to keep up and reply to all posts by customers is that the more comments that are on your status, the more people who will see your posts.
So, remember to monitor your Facebook and Twitter page daily. Respond to any questions and comments. Even if someone just posts that they love your product - make sure to thank them.