I think OOCSS has a strong influence on this use of multiple classes instead of your example of nesting classes (which i would have done, too). I'm not saying

I think OOCSS has a strong influence on this use of multiple classes instead of your example of nesting classes (which i would have done, too). I'm not saying I totally agree, but OOCSS promotes the idea that your styles should be decoupled from your HTML structure. This makes CSS easier to maintain.