A person who appears to be an activist on a social networking site such as facebook or twitter but that is the only place it happens. Kind of like a keyboard warrior, they are only an activist on the internet.
You get a lot of this around national disasters or for causes like cancer.
Used by people to make it seem like they care about something to impress others.
Someone's status update: insert any concept here 97% of people won't re-post this, the 3% who do are my friends.
Me: This guy is such a fucking internetivist.
Month's like, Change your picture to your favourite cartoon to support AIDS research in Africa.
Me: I'm sorry, how does this do anything at all?