Well when I started on the net way way back , when it was quite a minority thing here at the time, I "met" a good friend who was older than me but we chatted most nights and he e-mailed me at work even, So he was always around in some way or other.
He sent me an e-mail on a Sunday night I think it was and that was the last I heard from him. A few weeks went by and then I got another e-mail from a woman I didn't know. She was his niece I think. She asked me if I knew him, so immediately replied saying yes and haven't heard for ages.
She wrote back and told me he'd died!
I'm not at all religious but she wanted to send me a prayer card in his memory. I of course said yes.
I was actually quite upset, even though you don't meet someone in person they can still become close.
I've always treated online friends just the same as any others.