Every so often Google will do a little "re-think" of it's algorithms for deciding Web site rankings. They are sort of like earthquakes. After a period of quiet, all the Web community starts to get a little nervous about what might be afoot. They know that another earthquake is overdue. The SEO community tends to call these little changes hurricanes rather than earthquakes and even gives them names. Blog Business World has a pretty good explanation as to why some major Web sites went down a notch in Google rankings while blogs seemed to do quite well.
The recent Google update, referred to as "Florida" around search engine optimization (SEO) circles, had an adverse effect on many link trading websites.
Blogs trade links extremely frequently, often almost obsessively so. The blog link trades were not affected by the Florida Google update. If anything, blogs benefited tremendously. Bloggers are really generous linkers. They literally link to Everything. Because of their heavy outlinking practices, their often large lists of links are not seen by Google as a possible "link farm".