Web Marketers seem to make the same mistakes (over and over) when looking at organic search traffic. I mentioned 6: not filtering out the CEO, assuming job seekers traffic should convert, giving SEO all the credit (I wish!), assuming all unpaid traffic is 'organic', misinterpreting what is happening in other google lands (ie google.de), think all they get are brand name searches. Presented at emetrics New York 2011 to rave reviews.