There has been much discussion about pseudonymity and real-name policies in the wake of Google+ (I'm on it! Come say hello!), and what expectations different groups have for online interactions.
I didn't meet the internet until I started college. I didn't get email until I started college. I'd guess about half my peer group (Gen X) was about the same, though among my friends (geeks with a high fraction of CS/math/physics types), I was late to the party. They had 512 baud dialup to BBSes and whatever. I couldn't figure out how to play Oregon Trail on the high school computers. I'm sort of the generation that had a lot of formative experiences in meat-space before the internet really took off. (I know people who are a decade younger than me who say they're "from the internet.")
Yet I have many friends online, some of whom I've never met in person, but I see pictures of their kids or pets on facebook or twitter. I received a box full of Turkish media (books and DVDs) in English from an almost-complete stranger who offered to send me some things to help me understand Turkish culture better. (I was expecting, like a book or 2. I got 5 plus 3 DVDs.) I commented that I love German Christmas foods, and an acquaintance sent me a care package full of marzipan and Lebkuchen and hazelnut chocolate. I hope someday to return the favor, or pay it forward to someone else.
I have friends who I met online and have become close friends, with whom I share trials and joys, to whom I offer support and congratulations. Some of them I've since met in person, but many, possibly even most, I haven't.
I met my husband via the internet, through some people I met in person who had an IRC channel they hung out on and a mailing list.
Thanks to twitter and the German football league, I have casual friends who live in Norway, Pakistan, Egypt, and Bangladesh, as well as Germany and various places in the US and Canada. I talk with fans of my club team on twitter, and the next time I make it to Berlin, I'll see about meeting some of them in person. (To catch a match at the stadium or in a bar, whatever.)
I've been online for seventeen years now, close to half my life. I became more involved in the internet about thirteen years ago, when I met the people with the IRC channel. I've had a dozen online identities since then, on mailing lists, general forums, topic-oriented forums, blogs, communities. I currently have seven different handles online, some more public than others. I don't make it a secret that @exaggerated and @strafraum are both me, but @exaggerated is where I put pictures of my cats and links to my blog, and @strafraum is where I talk about (FIFA) football.
Where was I going with this? Right. I think online is where a lot of people have formative experiences, develop deep friendships, and generally interact with other like-minded individuals. It's so much easier now than it was twenty years ago to find other people who like reading/writing the same kind of stories you do. I've wondered so many times how my high school life would have been different if I'd had access to the internet, or even known that there were other people out there who liked SF/F. (A much less trivial aspect is that LGBTQ teens in small towns can find support online through various communities and know that they're not alone.)
Oftentimes, these experiences take place under a pseudonym, a handle. The handle, once used long enough, becomes as real as the name on the driver's license or birth certificate. It's a name we choose, not the name we are given, and that's as real to us as the name our parents chose for us at birth -- and sometimes more real. People legally change their names for a variety of reasons, and whether it's because they hate their birth name or because they're transgender and their birth name is wrong, those are equally valid reasons.
The first link in this post discusses who is harmed by real-name policies. The answer is anyone who is outside the societally-accepted norm.