I believe that online friends are a different type of friend, though no less valuable than a 'real' friend. Not being able to see people's reactions etc. makes it difficult to say that you really know someone you've met online. However, it's easier to communicate your feelings/problems with online friends because you're physically distanced from them.

I wouldn't say that I know my online friends as well as my offline ones, but I feel just as comfortable talking to them as I would my friends in real life. As for who my online friends are, I don't want to risk leaving anyone out, so I'll just assume that you know who you are already.