Does it seem like social networking changed the idea of friendship to the point where someone you may have never met in person can be a better friend than someone you meet? It's not only changed friendship, though, it's expanded the numbers of friendship. I'm not sure this is a good thing. For example, a new study says that if you count all the "friends of friends" you have on Facebook, it would "reach an average of 156,569 other people." The median user's "reach" is about 32,000 people if you count friends of friends.
What does this mean? I think any time you throw around big numbers like these with regard to friendship, whether it's for social networking or not, it can seem falsely encouraging or genuinely lonely. It can make people feel like they either have a lot of friends in their life (which maybe, if you consider the real definition of friendship they don't), or it can make someone feel bad if they aren't pulling numbers like this in on their Facebook page.
To me, these numbers don't mean a whole lot, but the reality is that if you did need to determine your "reach," it would be with people who were genuinely your friends and then people who were genuinely friends with them. In other words, people who you could put in a room and talk to if you needed to. As we know, none of that exists in the social networking world.
I encourage you to keep your view of friendship, real friendship, to people who have either met or corresponded with at length in the online world. This way, when you need to reach out to friends, you'll know where to look.