To add:

There might be people who do not need social interaction, but then, they are invisible to others - whatever they do, be it knitting or engaging in Zen silence, they just keep to themselves.

If a person, say, knits and simply posts images of her creations online, even if she does it in pre-Web2.0 fashion i.e. on her homepage that does not even have interactive functionality (as opposed to blogging with comments enabled), she is still being social, because she cares enough to let others have an opportunity to see her work.

To the extent that you have a need to post, you are clearly social.