Online communities hurting "real" communities?

I’ll admit it, I’m an extreme introvert. Not only am I uncomfortable in social settings, but I’ll usually go out of my way to aviod putting myself in such situations. It’s a psychosis that my wife, a textbook example of an extrovert, as well as most other extroverts just cannot fathom. Some would say that I don’t enjoy people, which isn’t the case. I very much enjoy relationships with others but I also fear the process of getting to know someone that well. I know, it’s a little strange.
I tend to open up to people very quickly electronically; maybe I’m afraid of the vulnerability of face-to-face communication, I’m not sure. Either way it’s very annoying to me (and I’m sure others sometimes). But, is this problem being worsened by my participation in online communities? Would I grow better in face-to-face situations if I didn’t have the excuse of communicating with people online? I’m not completely sure that I would due to the sheer number of social settings that I’ve been in compared to my relative comfort level in such situations. It’s an interesting question to ponder though for we introverts.
I’m not so much talking about the people from all corners of the Earth that you’ll likely never see, I’m talking about the people that live here, in my county and most of the time even in the same city as me. There have been several cases in the last few years where I’ve see someone that I’ve interacted with on a fairly regular basis electronically and I’ve felt very uncomfortable.
Here’s a real-world example. One of my Flickr contacts is a local woman who happens to be a pretty good photographer. She’s around my age and has a lifestyle that isn’t alltogether different from mine. A few months back I was in a local coffee bar and happened to see her across the room. I’ve never met her officially but we’ve communicated some online. Seeing her I was instantly afraid that I would be confronted in some way by her. I worried that she would want to talk about my photos and (gasp!) I would have to communicate! So, I spent the entire evening focusing more on avoiding a confrontation rather than focusing on having a good time with the people I was there with.
These types of situations don’t happen to me often (and I’m probably making it sound like a bigger problem than it really is) but nonetheless it does bother me. And I can’t help but wonder if I’m making the problem worse by being so involved in these online communities.
Do you have any similar, unjustified fears that you worry you’re promoting by your participation in online groups? I’d like to hear about them.