Barry Schwartz Wrote in his site searchengineland.com that Google has an improved algorithm to fight web-spam. I am watching the SERPs closely recently and I have noticed that there are less of a non-relevant results but still it seems like a futile fight. Matt Cutts, the head of Google's Spam-fight group and a senior speaker for the company has provided the amazing data that 80% of the new webpages to be found by Google's crawler (/spider) is content which posses of a low value.
Spam is only common in certain, sometimes dark, areas of the web, where a lot of big money is. There's a very low likeliness that it would be found someplace else and especially for information queries in most fields. So, since the web-spam group of Google consists of 1000's of people, why wouldn't they go manually over the top results and sort it out a little. I was assuming they are doing just that, but I am proved to find it's the other way around. Superb results that use to be in Google's first page are now gone, replaced by direct domain names with low quality content (a rewrite of generic templates of such sites, on most cases).