The perception of someone is an amazing thing in our culture. People perceive others in very special ways because of how they represent themselves. This is also true for bloggers, and if you want to be the big shot blogger, you have to walk the walk. The authoritative blogger asserts himself or herself as thus.
I believe a blogging authority is an author that people will look to for advice, commentary, and information on any particular subject discussed by the author. This person should also earn the respect of a majority of his or her readers, even if they do not particularly agree on a particular issue. However, all people have the potential to become an authority.
It is all about how people perceive you, and you should create this perception by being professional. You need to create a great image for yourself, as when it comes down to it, you and I are just bloggers; however, as I am writing for this blog, people will generally perceive me as an authority on what I am writing about. People, at the very least subconsciously, are very likely to perceive me as an authority.
You will need to have a certain amount of professionalism about your work and the way you act if you expect to achieve greatness in the blogosphere. Perhaps authority and professionalism are closely related, but they are very different; however, having both would be the ideal situation. Lying, over advertising, being gimmicky, and many other things could harm your chances at ever establishing yourself as an authority. But, this also requires some brain power.
Having knowledge is a great way to have people respect you, but only knowing the facts is not good enough. You should be able to answer the question of what, why, and how as well. If you can provide people with in-depth information, you will be seen as a much more knowledgeable, reliable, and valuable resource to those which have read your material. Also, someone that has been willing to put in the research to gain the knowledge about what they are discussing will show in the finished work.
Finally, if you are going to be an authority, you must put the truth ahead of all else. Like a journalist, the truth and your readers should come first. If you build a name for yourself, it is just as easy to have it crumble from a single lapse in judgement. Build your name, protect your name.
Hopefully you understand now that it is everyday people that have built their authority. How else do these sites like Joystiq, Scobleizer, TechCrunch, and ProBlogger get built? The authors established themselves as an authority. The only question is when will you establish yourself as an authority?