Depends on the particular program vendor. Check what program they are using. Right click the top of the columns & choose to show type/vendor so it shows which program they are using. Some programs out there are too aggressive & don't stick to gnutella protocol. They bump others out of the way to get to the top of the downloading list (your upload queue). If it's a known bad gnutella program, I think you could right-click them & choose ban. I may be wrong.