[dementrium]

This advanced mathematical problem can be explained by a simple scenario.

Example

Let's say a tracker start from scratch with 3 users (A, B and C) and a 1:1 ratio requirement.

User A uploads a show.
User B jump in and complete. Then, A drops with 0 down/1 up.
User C jump and complete from B. Then, B drops with 1 down/1 up.

End results

A = 0 down/1 up
B = 1 down/1 up (1:1 ratio)
C = 1 down/0 up (0 ratio)

Which lends to...

A = ratio vigilante (and possibly with a double moral looking at his DaD ratio).
C = banned.
B = Ok. Just wait for user A seeding a second show. After that, B will be banned as well.