I don't see how they're a hindrance unless an otherwise "socially-able" person socialized online to the detriment of their offline social life, job, or studies.
Despite being active, I have no offline friends so the only company I have that isn't at an acquaintanceship level is online. There's something to come home to after studies and someone to care about my health, my ideas, and my worries when I want to talk. Just having other human beings to interact with who are actually part of your life can make a difference, even if you live a thousand miles away. That can still be a friend and the effects of mutual compassion and giving are very real.
I've stopped trying to make new ones, though. After one online friend has avoided you after meeting in-person and people don't want you offline, it's hard to trust new people or feel that they don't just like you because they haven't met you. All that sitting at the computer typing while others are out sitting around tables in diners and laughing, and they might still not like me past the initial impression...