I'm a couple of days behind in my blog reading, and I have reached a conclusion about blog branding:
A great blog brand means that you have right of first refusal on my limited attention and its ever-shortening span. It means that I have learned from experience that if I have 156 RSS feeds and only time to read 15, I will visit your blog first. You've earned a top-of-mind position. I can count on you to entertain and enlighten me. My attention is yours to lose.
And since your blog content is free, the "economic goodwill" you accrue with me is that I will visit you more often, spend higher-quality attention on your blog (perhaps even commenting), and more readily believe what you have to say. Plus, I might link to you in my posts, tell my friends about you -- or even blogroll you as a way of credibalizing myself to my own readers.
Now, the key to building a great brand is to be consistently great. Imagine if everytime you popped open a can of Coke, it was better or worse: Sometimes salty, sometimes sweet, sometimes fizzy, sometimes flat. A crap shoot. If anything, Coke's brand would become known for its inconsistency. Not good.
In the blogoshpere, greatness of content is subjective, defined solely by its relevance to the reader. I won't get sidetracked about what makes content great. It's an opinion thing. But consistency matters to everyone.
But if your content starts to become consistently less relevant to me (or less edgy, because I like punchy, authentic, informed, high-quality content), then you risk my learning to pass you over in favor of other blogs who seem to be consistently "more" of these things.
Sooner than you think, someone takes your place at the top of my mind when a colleague asks me "Who's blogs do YOU read?" Stick your fist in a bucket of water. Now take it out. With few exceptions, such is the impact that most blogs have on the world around them.
Bottom line: You have (+/-) 5 posts before your blog's "brand attention bank account" is overdrawn. So spend my attention wisely. You can be replaced in a jiffy.