the internet just isn't the same as real life social interaction.
The big difference is it's huge. Even individual fandoms, for example, have several different branches, sites, forums, mailing lists, etc. If someone keeps annoying you, or you get fed up of how one board is going, chances are you can find somewhere else to hang out with people who have the same interests as you.

If you don't get on with a work colleague, classmate, or neighbour, you can't just up and move that way.