I've just started reading William Zinsser's On Writing Well: The Classic Guide to Writing Nonfiction and I came upon this little gem of a paragraph I just had to share. Back when I was doing my undergrad, a rhetoric prof of mine kept expounding the theory of economy (as it relates to writing), and I've been a believer ever since. Zinsser spells that theory out, very clearly (p. 7):

"...the secret of good writing is to strip every sentence to its cleanest components. Every word that serves no function, every long word that could be a short word, every adverb that carries the same meaning that's already in the verb, every passive construction that leaves the reader unsure of who is doing what -- these are the thousand and one adulterants that weaken the strength of the sentence."

In other words: keep it simple, stupid.