First, I haven't noticed any significant increase in the frequency of spam sites appearing the Google search results. The biggest problem that I did notice is s

First, I haven't noticed any significant increase in the frequency of spam sites appearing the Google search results. The biggest problem that I did notice is social bookmarking sites, like reddit and digg, outranking original content. They often have nothing more than a copied-and-pasted paragraph, sometimes supplemented by low quality comments (as is common with these types of sites). Since this site is very similar, not many people will be concerned about this issue. Second biggest issue is poor Wikipedia articles appearing in the top results for almost any reference type query. Many less frequently updated Wikipedia articles are nothing but regurgitated content lifted from other quality sources. What makes it worse is that Wikipedia is using no-follow for their links, so even if these sites are linked in the reference section, they won't get any credit. It's interesting to see so many people complain about low quality content on commercial sites, but they never mention Wikipedia, which is a much bigger offender (I guess this might be because Wikipedia gets its content for free and doesn't have ads and other sites pay for the content and do have ads). Third, I hope Google doesn't make any changes without checking very carefully that good sites will not be negatively affected. For example, newspapers will often have the exact same articles from the AP, but also original content based on their own reporting. Punishing them for having duplicate content would not work well. There are many similar possible pitfalls.