1) A successful brand has a unique selling proposition that differentiates itself from the others. Similarly, a successful blog will be different from your run-of-the-mill indulgent online diaries. There will be something unusual which drives hordes of fans to your online space every day (or night).
2) Pioneering brands get the biggest bite of the cherry and occupy the biggest market share. Similarly, blogs which have moved into the game early tend to attract the largest following.
3) A brand will only be remembered if it has a distinctive and memorable personality. For example, Harley Davidson will always be associated with a rebellious image, while Volvo will be remembered for being safe. Likewise, blogs which are successful (at least measured in terms of visitorship and page views) tend to have strong personalities and are often an embodiment of what their creators are like (whether explicitly or implicitly).
4) Brands, like blogs, need constant investment and nurturing to keep them going. In the case of brands, it includes advertising, publicity, events, and other tools in the marketing bag. For blogs, you will need refreshing content, links, posts to blog aggregators, and peer-to-peer communication to keep it alive.
5) Branding is an art. You need to have creative juices of your best designers to inspire and leave a deep impression. Similarly, blogs which have captured the imagination usually have either poetry in words, beautiful pictures and a nice overall aesthetic.
6) Branding is a science. After creating a strong brand identity, you need to look at disseminating it through the most productive channels. Likewise, hardcore bloggers know that some of the technical bits help generate traffic - number of pics, length of posts, RSS feeds, links, trackbacks, etc.
7) Good brands engender loyalty. You don't just buy a Prada bag or a Mac computer because of design or quality (though that certainly helps). After some time, a certain fanaticism kicks in. Similarly, blogs which have big followings have an X-factor that draws people to tune-in on a regular basis. They have that resonance with their readers on a long-term basis.