I think everyone at some point has had a bad experience trying to communicate with a business. An example I think everyone can relate to is say you go through the drive thru of a fast food establishment, order, get your food, and leave, but not before checking the contents to make sure your order is correct, only to find it's the wrong order. So you park and go inside, only to have the manager say you're wrong and you can't do anything about it. Maybe I'm projecting a bit.
Social media can make it easier to get your problem solved, depending on the platform and the company. Yelp, for example, is a great platform for food establishments to take criticism and can be a good way to have your issue with the restaurant taken care of.
I have never attempted communicating with a business through social media, as I'd rather complain about a problem in person, but I have seen examples of people having positive communications with some businesses over social media, particularly if that person has a large enough following.
I would respond to negative comments on my business's social media by not attempting to argue with the unsatisfied consumer, as most of the time the mob that is the internet will side with the individual rather than the business, and that can leave your company in a negative light. That's why the phrase "the customer is always right" has some truth to it, you never really should argue with the customer so you can keep them coming back.
