Orkut

The most obvious disadvantage of the DIV tag is the fact that it doesn't aid in adding semantics to the page.

The DIV tag is a generic holder of content. As such, a parser has no understanding of why that content is being pulled out and place in its own container. For instance, in XHTML, the DIV tag would have been used to surround this question and answer block, allowing the page authors to add CSS styles like a set width and colors.

In HTML 5, we have more specific container tags that make it easier for a parser (like a search engine) to understand the way the page is laid out, and determine what information is important, and what information is secondary.

In this page, and ARTICLE tag would be the best choice to surround this Q&A block. ARTICLE indicates that the content is syndicatable and that it's the primary information on the page. The menus would be added with NAV tags, allowing a search engine bot to recognized what their function was, and act accordingly.