Good point, and it raises an interesting question.
Is Facebook really that much easier to understand than e-mail, usenet, and IRC? Or is Facebook just better at marketing?
When my Mom wanted to get on to Facebook there was definitely a learning curve. She had to be shown by my sister and myself how to do everything... sign up, post photos, learn about what a "comment" was, how to add people, manage things... Facebook is quite a complex piece of software. I don't necessarily think that Facebook requires less technical skills than decentralized services.
In my opinion, the reason Facebook is popular across all demographics is because it is based on real identities. Real names, real faces. Before Facebook the Internet fully embraced anonymity and this requirement to partake in role playing, having an avatar that was separate from yourself, was confusing and a little bit terrifying to older people. My mom would always wonder WHO I was talking to on the Internet. They could have been a murderer, or a kidnapper! If you can't see their face or know their name, she thought, how could they be trusted? My parents are NOT on Twitter and will probably never be for similar reasons. It is too weird for them to think about having a separate personality. They weren't stage actors or used to the public eye because they were raised in a very different media environment. The distributed Internet turns us all in to celebrities. Facebook keeps things the way they were but allows people to benefit from the same abilities to publish, just to a seemingly private group of close friends and family.
Facebook, in my opinion, is a nice little service to hold your hand while introducing you to this very different new world that is emerging.
On the topic of marketing and technology... I'm just going to use Sun and Java as an example because I was recently talking about this and it's fresh on my mind. Sun did an amazing job of marketing Java on the Internet. In the mid 90s every other web page had that little Java mascot on it. They took the Internet and ran with it, big time. There were much better and much easier tools around but their creators didn't do enough to evangelize their benefits. You gotta get out there and sell this stuff to people.
It took open source software a LONG time to realize this. Products will wither and die without proper marketing and advertising, no matter how much better they are.
"Great marketing and decent technology gives you a better bandwagon than great technology and decent marketing", as said by Ralph Johnson at http://c2.com/cgi/wiki?JavaVsSmalltalk - which BTW, is a great little wiki full of interesting conversations from a bunch of old timers and academics.
