Here's an interesting article I found on another site about the effect of rinsing your ground beef. It shows just how effective it is for removing fat.
http://foodsafety.wisc.edu/assets/pdf_Files/Reducing%20Fat%20in%20Ground%20Beef.pdf
http://foodsafety.wisc.edu/assets/pdf_Files/Reducing%20Fat%20in%20Ground%20Beef.pdf