Best:
We meet new people with different backgrounds, ideals and mindsets. We learn new things and continue to learn more; acquire it and help us live our real life, away from the vast world of internet. We become better version of ourselves (I hope).
Worst:
You can never hope for too much. You can never expect that there will be something more out of it, beyond the screens of your phone and computers. You'll end up meeting good people, becoming friends with awesome ones or loving a person; but at some point in time, the relationship may become over, you can be blocked, history can be wiped out or worst you can just be 'seen' forever.