All businesses should have a social media presence and this is especially important for small or start up businesses wishing to build their brand. The beauty of social media marketing is that most of it is free apart from your own time.
To use social media effectively you need to be able to take the time to build up followers and respond to people that contact you or mention your company. You should always reply to people as you will find that you build up a group of followers a lot more quickly.
Some businesses are put of by using social media thinking that there are too many people out there that will just use it to vent about frustrations or issues that they have with the company. My answer to this is that it is always better to be aware of any issues that a customer may have and have the opportunity to rectify and respond to it.