be efficient, be frugal with memory usage, etc etc. But those rules just don't apply anymore, at least not to such a degree that they used to.
The above may not apply to simple programs and small sets of data, but somewhere out there someone IS pushing the envelope and guess what, it turns out all of those things still do matter! And they always will, because no computer can ever perfectly recreate the universe and run it in real-time. You should try dabbling in 3D computer graphics sometime to get a feel for how much further we have to go.