The disadvantage of social network is the most people don’t know how to network effectively. As a result, the few benefits they get from their networking activity are not worth the time invested. The best way to avoid being disappointed in this way is to decide on a strategy for using social sites, and stick to it. For example, if you are going to use Twitter to draw attention to exciting new content on your website, then resist the temptation to waste time tweeting about unrelated topics. Stay focused on what you want to achieve and don’t let yourself get distracted.
That I said at the beginning social have two sides are good and bad, so before you will use them you have to know the effect of them, ex. When you talk with someone that you never know on social you have to be sure he or she is not a criminal.