We noticed today while testing overdues and fines, that leaving the overdues fine cap empty means that fines will accrue indefinitely. Before this value was moved to the circulation matrix it came with a predefined value in the sysprefs, so we never ran into this. I am not sure how we can resolve this, but for people just starting using fines this behaviour should at least be documented and it may also be good to have some kind of warning.
... because if you have really old overdues in your system that means that you might run into trouble with the fines script generating the fines.
To me this is invalid, it seems to be the expected behavior.
I think the problem was that my fines.pl script unexpectedly created a few thousands of fines - but as noone has reported problems with this behaviour since, I think marking WONTFIX is alright.