To people who don't spend time at community-oriented Web sites or on Usenet, friendships formed there have a certain sense of unreality. Mostly this is, well, the older generation (not all of the older generation, nor even most, but many), but coevals who haven't embraced the power of the Internet often have the same perspective.
They can't understand what could lead us to spend so much of our time at such places—they don't even understand that they're places. They use the Web, if at all, to look up facts or read the newspaper.* They don't see the point to online interaction.
Are people on the Internet real? Well, I'm on the Internet, and I'm real. I suppose it's possible that everyone I think I'm encountering is just an AI, but it's not likely.
I met my first girlfriend on alt.folklore.urban. I met my second on Livejournal. They're both real.
"But they're so far away! What could you possibly have in common?" Well, one blessing of the Internet is that people who do have quite a few things in common can interact even if geographical area—or even continent—is not one of those things.
True story: I started reading someone's Livejournal through the usual chain of recommendations, and certain references in her journal led me to ask certain questions. Long story short, she lives four blocks from my parents.
Inspired by prole's write-up under "Trying to explain Everything to your non-Everythingite friends." Thank you, prole.
*Come to think of it, I have no idea how people use the Internet non-interactively.