Which is that clients can’t trust each other and trackers should not trust clients. The ONLY data being exchanged is actual data and address/port information. The data is checked via checksum, and well adress/port is checked by if you can actually connect to the client (or tracker).

Any attempt to add data for ratios means somebody can cheat or lie.

I’m behind BT. Leave it alone. It works BECAUSE of the paranoid model!

If I download a set of rarer, unpopular torrents, I may not find people to upload to. As a result my share ratio suffers and I am prevented from downloading new files. The tracker only knows about files that it tracks, thus if I only downloaded unpopular torrents from the tracker, I may NEVER be able to recover my share ratio now matter how much I want people to uploade the unpopular torrents.

If a torrent is widely seeded, a similar situation arises. When there are more people uploading then downloading, few downloaders are downloading from me. It may take an enormous amount of time to recover the share ratio.

In neither scenario above was the victim peer misbehaving. They are simply scenarios under which share ratios should not be applied.