I actually support the idea of a ban log...but one that indeed is only viewable to staff. If in the case of someone who was banned a long time ago, and the staff has changed, wouldn't it be important to know the original reason? Also, in the case of a person creating multiple accounts to evade a ban shouldn't you keep track of all the duplicate accounts being created for IP blocking purposes?
I mean maybe it's not needed *now* but later on you, you might wish you had it, so that you could keep an eye on someone who registers with another banned users IP. And IIRC, you can view the ban log in your ACP, so maybe another one is superflous, and if so, then yeah, don't worry about it. As long as you have a copy somewhere to reference when people are asking why a particular IP was blocked (especially in the case of someone blocking an IP that an legitmate member uses) that works, IMO.
Having Corel Prison is pretty much useless though, as quite clearly it rarely, if ever worked on ACF. The concept itself is good, but it just doesn't work in practice.