Typing in a wide variety of keyword searches in my particular niche will lead you to some pretty awesome sites, many of which offer regulars the ability to buy and sell directly to others in site classifieds sections.
Unfortunately, if the words "for sale" are added to a search for ANY of these items these sites no longer appear in Google, at least not until page 3-4. In their place are aggregating sites, mashups of classifieds from all of these sites scraped without permission.
To get a top ranking in this niche Google is very clearly saying offer mashup from multiple sites, the results are 100% dominated by these types of aggregate content sites.
Even Craigslist isn't immune to this. Several of the top ranked sites offer Crigslist ads almost exclusively, complete with links to the craigslist classified page the content came from. The problem with this? It's against Craigslist terms to be stealing their ads.
I think Google needs to pay attention to this a little more closely, otherwise what is the point in creating a great service if a mashup service will steal your thunder(visitors) with your own content? It's a real problem right now, Bing and Yahoo are not nearly as flagrant right now in this field.
