Yes, there are real social networks online
One would think that with our increasingly networked lives, via blogs, IM, email, myspace, and the like, people would be more connected than ever, but that seems not to be the case. A person can have 200 friends on myspace, but no one to talk to when faced with a scary medical situation, for example.
I find this fascinating and a bit boggling because it is the *complete* opposite of my experiences online. Because of various online groups, I have a very large network of people I can call on: to meet when I'm in a strange city, to give me medical advice, to complain about something that's bothering me, to cheer about something good, to discuss problems with my work, my children, my finances.
There are three factors that may make my experiences different from yours (or those of the people in the study):
1. I am female, and we're taught to be better at social networking and to be more willing to share our problems than men are.
2. Much of my networking is at LiveJournal. LJ is especially popular with women (I estimate at least 80% of their users are female) because users can filter posts to be seen by only certain people. (Women are subject to hugely more harrassment online than men are.)
3. I am part of media (TV, movie, book) fandom, which has always been a vehicle for friendship as well as mutual hobbyism (if that's a word). That is, we don't just share an interest, we share aspects of our thoughts and personalities.
When online media fandom was largely on USENET groups and mailing lists, fans would occasionally "band together" to help out or celebrate a fellow fan: sending things to people in the hospital, giving travelers places to stay, making e-gifts to celebrate the birth of a child, fostering pets, for instance.
On LJ these activities have continued, but under friends-lock I've also seen the growth of more serious helpfulness: hospital visits, monetary help in a financial crisis, legal help, moving help, housing. Because the number of people helping can be very large -- into the hundreds -- the burden on each helper can be kept managable.
It's not the Internet, it's what you *do* with the Internet.