Socially insecure people tend to gravitate to online socializing because they have more control over the amount and timing of their interactions. Reducing face to face interactions tends to reduce social anxiety for less extroverted individuals. Unfortunately staying within your comfort zone, limits personal growth, and prevents the development of valuable face to face relationships.
Don't have something to do tonight? Instead of commenting on everybody's Facebook statuses, give somebody a call and go out for a drink, you would be surprised how much better it feels to talk to a real life physical human being.
If you are single and feel like you need a significant other to be happy, I am going to be blunt, YOU ARE WRONG. You can't be in a healthy relationship until you are happy independently. Using somebody else as a crutch for your happiness is a one way trip to an unhealthy relationship. If you are struggling to find a companion, stop looking in bars and stop looking online. Consider joining activity clubs for singles or participate in a group activity that encourages socialization. You will meet like minded people who share more in common with you that booze or Facebook friends.