Originally Posted by cordelli
And they get other pages to link to you. Lots of pages linking to you give you a better ranking:
You might check to see if the number of other sites that link to your URL has decreased. This is the single biggest factor in determining which sites are indexed by Google, as we find most pages when our robots crawl the web, jumping from page to page via hyperlinks. To find a sampling of sites that link to yours, try a Google link search.
hence link spamming (like when you search for say a camera, and find a bunch of near-identical sites like buy-gadgets-now.com, camera-store-1.com, get-cameras-here.com)
looks like google has managed to dilute the effect of link spamming, but it's still a factor