The web has changed and so has the way Google indexes and serves up web pages. Read the evidence in Google’s official webmaster blog.
After reading this article in Google’s blog you may have a better understanding of the importance of real-time relevant information that comes from regularly updated sites such as news sites and BLOGS.
Yes, blogs have become a very important factor in SEO for your main site. Creating links in your blog that relate to information in your main site can be very beneficial not only to the indexing of your blog but also the indexing and positioning (SERPS) of your main site also through relevant linking.
Social media has also become a perfect place for search engines to index real-time relevant information also. Many people build main websites and never change content. This means the information in these pages can become outdated and not as relevant as information posted in a twitter post, on a facebook fan page, or on your linkedin pages.
The Caffeine update is complete and will change the way your pages are indexed and ranked in the search engines.