I think that this is getting into an ASRG question.
If we create a graph of false positives vs false negatives we get
an L shaped curve for most filtering technologies that are
parameterizable and a point for a non perameterized technology
such as a blacklist.
Rather than arguing this point round and round does anyone have
a ready made graph with the various blacklists plotted on it so
that we could make a useful comparison?
There are two reasons why a list would have more false positives,
the listing criteria/application thereof could be wrong or the
list could be more aggressive in listing more spam sources.
If List-A listed 100 addresses and 80 were wrong this would result
in fewer false positives than List-B listing 1,000,000 addresses
with 800 wrong. So there is a discrimination function here...
We got a lot of false positives with the SpamCop list, and other BLs
are bound to be worse.
Actually, Spamcop's list is infamous for its vast number of false
positives. That's why nobody I know uses it for anything more than
a fairly low-weight input into a scoring system.
Try the Spamhaus SBL and XBL and you'll find very few misfires.