Um, the person *IS* sharing files or they wouldn't be getting retries.

There's only so much upload bandwidth to go around, and once all your upload slots are full you'll get retries. Increasing the upload slots too high doesn't help - it just makes everyone's transfers so slow that no one will download sucessfully from you.

What hurts is when some luser decides to hammer a busy peer every few seconds trying to download. that just eats up bandwidth for everyone.