Having looked at a lot of HTMLs, I noticed that sections are not really the default. I rely on headings (h1, h2, ...) to chunk each pages. Each chunk has its heading hierarchy attached to it. There are a lot of optimizations that could be done at that level.
i'm just guessing but i would think following whatever semantics leads to the highest search rank in google's algorithm would be what you're most likely to find out in the wild.
