There are also the people who aren't necessarily your best friends, but who you just seem to spend a lot of time with: Co-workers, teammates, people you volunteer with. Again, it's all about the randomness of just being there.
Blogging and the web bring with it an interesting dimension, because the life that only a select few used to be privy to is now, more and more, being consumed by all--indiscriminately. You can't really treat any of your blog readers as special because they're all getting the same content. Sure, maybe you could direct message a Twitter friend, but building a really strong friendship 140 characters at a time isn't ideal either.
I recently shared something pretty sensitive with a slightly more professional friend that I don't get to see all the time and at first she was kind of taken aback. She didn't know what to do, because people don't usually just come out and share the information that I showed her. The fact of the matter was that it was one of the few important pieces of content I have that the rest of you don't get to see. Contrived, perhaps, but I showed her because I wanted to say, "Hey, listen, you're the kind of person I want to have in my life and life's just not naturally bringing us together in a friendship the way I want it to." That happens a lot and sometimes you just have to nudge things a little.
Building up relationships and trust is easier than you think because of online tools, but building that small set of just a handful of people you can really reach out to and depend on is almost harder because of online tools. How do you demarcate the special folks when everyone else in the world gets to see most of what they do anyway? It's like creating a VIP section in a theater that only goes 5 rows deep and is completely in the round.
So, at least for a moment, I found a way and formed a new bond based on exclusivity... so just keep in mind that as much as you all think you know about what goes on in the other side of the blog, someone got to see something different that I don't think I want to share here. My world isn't totally flat... yet.