buckworks - 4:30 am on Feb 14, 2011 (gmt 0)
more sites that don't pass markup have superior organics than those that do
That's to be expected, as sites that don't validate fully are more common than those that do.
Valid HTML is not a magic ticket to the top, no arguments there. However, once in a while the wrong kind of error can prevent a spider from reading the page and that's a problem. Many validation errors can be safely ignored, but it doesn't follow that they all can.
Checking validation and fixing egregious errors should be considered common sense for the conscientious SEO.