[Loque]

Why bother with class 'bold' when you could use inline styles? (I jest)

I come from an older thinking that your HTML should not have any classes that imply visual style, and that classes/id's should be semantic to the content and structure of the HTML.

CSSZen garden is a good example of this.

Nowadays I personally love semantic markup, stylistic mixins, and a CSS file linking the two together following BEM patterns.

I think legitimate times when this falls apart, is when I watch the designers I work with now, work in HTML & CSS - they need to quickly move things around, so doing this all from markup gives them a big speed increase, up until a point that is. We get involved now early after initial client direction sign-off to make their markup and CSS more robust before they carry on like a pig in poo.