Not sure if this has been mentioned here but there are a couple of malicious ads around that auto-scroll the browser to view the ad. Doesn't seem to be a problem on Chrome, just Firefox/Opera. The two ads are:

sax...a.ca (weight loss products/medication)
gadg...s.com (Wordpress-based tech site with very little content)

Both have had thousands of impressions on my sites over the past week, for little monetary return, so they're probably bottom-feeding bidders.