A couple of years ago I joined a local gaming forum. We were a tight nit group and talked on IRC every week. I grew more attached to the users there, to one member in particular that I'd stay up at night and talk to him during his night shift, and after a while I joined them on their local meet-ups. I had a lot of fun and talked more with them, mainly on the IRC or through PM's on the site. I became really good friends with them and I actually went out with one of the members for more than a year though it was after I had met him in real life since we didn't really talk on the IRC or anything. I was friends with them for a long time and do miss some of them a lot.
Other than that, I've been very good friends with people I've met online and I also talk to people I know in real life a lot more online than I do in real life. It's a lot more convenient and I prefer talking on MSN or something than on the phone. I don't believe I can only be good friends with someone in real life, as long as they're interesting I'd love to be friends with them. Though there are some people I only know on the internet that I'd really like to meet in real life, to hang out with and everything.
For the gaming question, I have played with people I really liked but lost interest since it was only in that game. They didn't care enough to use MSN or something so meh.
Point is, I like people. If I talk to you, I like you and find you interesting. That's really all I'd want from a friend but I do have a small group of people that I really trust. I'm one of those "always have your back" kind of friends and prefer to have a few friends like that. If someone rang me, even an 'internet friend' at 3 AM and just wanted to vent then I'd be happy to listen. I'd hate for me to think of someone as a friend but they don't because we've never met in person. It shouldn't matter THAT much, you meet people everywhere. You might start talking to someone in a store or a bar or something, is it really that different? Sure, you know what they sound and look like but you're basically taking a chance. You do the same with the internet. Some people are great, others aren't. You shouldn't judge your friends by where you meet them.