Click somewhere on any page and drag up or down to select more text than the page shows. In most programs, this will auto scroll the page as you approach the bottom with your mouse. First noticed in August 23 and 24 builds; I'm not sure how far back this goes.
I can reproduce this at: http://www.nytimes.com/2008/08/25/sports/olympics/25volleyball.html but it depends on the height of the window. With certain heights, autoscrolling occurs, but with others it does not. At the url in this comment, resize the window so the bottom of the window is just below the paragraph: “It was just too much for me to take,” he said. “For the past few weeks, I’ve been kind of compartmentalizing my emotions. Finally, the filters came down.” and then select from: "BEIJING — While his players hugged and shouted and leapt into one another’s arms Sunday after the United States men’s volleyball team won its first Olympic gold medal in 20 years, Coach Hugh McCutcheon walked off the court, alone." on down. For me, this doesn't autoscroll in r35904. It does autoscroll in 3.1.2, so should be marked as a regression.
<rdar://problem/6172323>
I believe this is fixed now.