I've thought something along these lines too.

What happens is, when I first connect, I'll almost immediately (within the first fifteen minutes) get about three or four hits on the exact same obscure file... whatever the file du jour may be that day (varies between launches. I currently share over 7800 files). After a while, I'll see more and more upload-slots taken up with the same obscure file... every IP address different.

Since there are different programs out there compatible with LW ("Bearshare", etc), I've suspected that these other programs may use some technique of using multiple IP addresses in order to get around the "one person, one file" restriction I've set. I sincerely doubt 20 different people are all suddenly after the same copy of "funny-cats". (Though I haven't been able to pinpoint any particular netshare software as being guilty of this.)

It's always a video file too, but I suspect this is only because videos are the largest files, and the longer it takes to upload, the more likely you are to see multiple connections to it (MP3's just aren't big enough to prompt this "bug".) A really large document would probably reveal the same "bug" if someone were willing to spend 8 hours downloading a book.

Allowing multiple connections per user doesn't resolve the problem. It has the opposite effect, making it worse.

It can become quite annoying, as I see users wanting to download a simple 50K jpg waiting in line behind a half dozen slots taken up downloading a 700M video at 3K/sec. with 23 hours to go.