Some notes around the article I've just read from JZ; http://www.zeldman.com/2012/11/21/in-defense-of-descendant-selectors-and-id-elements/
Whilst OOCSS is the new hotness (or at least was a few years ago), I can faithfully agree with the notion of every element in your mark-up DOES NOT require a class... In fact use classes as a way to describe your mark-up where a descriptive/semantic tag ins't available.
By the same token, the use of an ID where appropriate is totally fine, as JZ
for instance with ID's seeing something like this in CSS is completely wrong:
#paraInsideAside {