Let's accept for now the wiki-truth that "Ethan Marcotte coined the term Responsive Web Design (RWD) in his article in A List Apart." Therein he recommends web designers acknowledge the ascendancy of the Mobile Web and develop presentations that are mobile-friendly to have the broadest possible accessibility. He proposes a solution in which "responsive web design" (#RWD) is the WHAT and fluid grids, flexible images and media queries the HOW.
We agree on the WHAT. We do not agree on the HOW. Here is WHY:
There is a place for fluid grids, flexible images and media queries, but they are NOT a firm foundation for #RWD. When employing the first two, for example, care must be taken not to waste resources doing things a mobile browser does anyway and better. And as Ronan Cremin explains, using CSS3 media queries rather than server-side capability detection relinquishes control over rendering while placing unnecessary load on smartphone CPUs.
WebDev wannabes from Bangalore to Boston are selling #RWD as WHAT and whatever they have to offer as HOW, but the wise will never judge a book by its cover: If responsive web design is what you seek, mobile-friendly Web 3.0 development is what you need.