Just to take a contrary view here about Google's motives. Big G is NOT trying to rid the world of 'spam,' it is trying to do what it has always tried to do, namely, muscle out small IM sites, be they good or badly written, from the top SERPs. Google wants a world where every keyword, no matter how obscure, yields a first page search result with Big Corp, Wikipedia, youtube, or other 'big fish' institutional site links leading the front pages, with little sites buried on page 100. It also wants to look noble while burying the little fish, so it keeps talking about a 'better user experience.' Whatever the cover, the aim is to bury the little guys.
I'll believe otherwise when a Panda change de-ranks a badly written page on an institutional site the same way it would when it appears on a minisite. One simple way to slap back an attempt to back engineer a spun article would be to manually rewrite an original article on a site (changing the sentence structures, clauses, tense, tone, et al), then spinning the rewrite before uploading the spins to directories and all. The spins then only lead to de-ranking the rewrite, wherever it is posted, and not the original.