Different kind of grief, because it's tinged (in my experience) with a certain weirdness. Not a "why am I grieving?" but rather a "what exactly am I grieving for?" ... because my online friends, including the one or two who've died, were just conversations to me. People yes but represented by text. It's weird grieving for text. And I've had semi-close online friends die but also super-close online friends vanish into the ether without a comment^. The latter is worse, because it leaves questions. ^these would be indistinguishable, I suppose, except that in the former case one receives confirmation. EDIT: great question.
Yes yes. I'm also unsure of what constitutes an "internet friend." Does that mean when we totally have the inevitable Hubski Meet-Up in Colorado, you guys won't be internet friends to me anymore? That's all it takes? A couple years ago I remember a girl that I knew on a hella obscure Earthbound forum met a guy on tumblr. They got super close, met in "real life", and now they're engaged, I'm pretty sure. At what point did they stop being "internet friends"? They skyped and played games together and everything. Are they still just "conversations" to each other at that point? Also, since I'm still butt-hurt about it - if you think grieving for online friends feels weird, but you liked the movie Her, your opinion means nothing to me.
That's the question I've wondered, myself. I think that depending on the interaction level you have with users, your silence at some point would be noticed and people would wonder. For those of us who are facebook friends or on Twitter, we might find out that way.