Do you think Google rates traffic and where it comes from? Let's leave out facebook.com where you tell your friends to visit your website and click on the ads. Only to find yourself with a locked/banned account. I don't even tell people on facebook.com about my website in fear of this happening. Only a few people in real life know about my website. Do you think it makes a difference where your traffic comes from? A safe place would be Google's search engine, but do you think it's biased in a sense? Have you guys ever wondered about this or am I just crazy?
Yes it matters a lot, especially if you get bad traffic, such as paid-to-click, paid-to-surf and even in massive newsletters where the http referrer will be empty. The best is traffic from search engine of course, but also from legitimate sites.