Twitter: A Micro Blog or a Social Network?

Hey all ye none existent readers? I have a question for you. Do you think Twitter is a micro blogging service or a social network. I have heard many people call twitter a social network, but I don't see much socializing. Yes, there is some, but twitter isn't built that way. Unlike Facebook (which I think is the purest form of social networking,) it is very hard to comment on other people's "posts" Yes it can be done, but I think the feature is still somewhat clumsy; You can leave a comment for a specific person, but you can't comment directly on another post. I personnel think Twitter mostly a hybrid, but in essence it is built as a micro blog.