Ha ha, silly. There's no such thing as a 'successful' blogger. Every time one is born it quits to go write a book.

But there are successful blogs. Melly at All Kinds of Writing discusses elements--consistency, shyness, laziness, drafts, aesthetics, written language, fresh ideas, vision, absense and diversity--that can make or break a blog.

More on this discussion over at ProBlogger (actually, where the topic originated.)