I wish I were that lucky but I'm not however I do know someone personally who gets near that traffic and like opmax said it's direct traffic.
I have one site that gets in excess of 100,000 uniques per month around 75% comes from the search engines
i agree most of the traffic is from search engines and those who get most of the visitors directly they are really lucky
Actually the best traffic you can get is from the search engines because those people are actually looking for you = targeted traffic
Why don't we track our traffic source? Google Analytics, Histat, StatCounter .... Don't need to ask such a question LOL
Search engines used to drive the most of any website traffic, however direct (viral) might make miracles