Although most large businesses have a presence on social media networks, it is not seen as a true necessity. Companies do tend to do things like getting on Facebook because they worry that they might be missing out on a good way to reach potential customers. However, this presence is not really believed to have a huge impact at this point. It is more of an investment in the future as companies are trying to figure out how/if they can use a presence on social media sites to actually increase the size and/or loyalty of their customer base.
I think it is a necessity for businesses to invest in their social presence. Although many businesses might not see positive results right away or at all, if your business can master the art of social media, there is a significant upperhand. There's a lot of mistakes that can be made when entering this territory, but with research, practice, and a keen sense of the value of social media, it "can help a growing business boost brand awareness, improve customer relations, garner market research, even bolster sales."