Ah, an old one which answers a question. Long live the search function.
Speaking of which: what's really lame is to reflexively shoot from the hip and ask a question upfront and firsthand to the author, expecting a personal firsthand reply, in blithe disregard of any meaningful effort to figure out if, perhaps, someone else inquired about the possible uses for those funny round things placed at the ends of axes underneath horse carts. Spending 10 minutes quickly becomes 10 hours, and much more, and that is simply past the point of reasonable endurance. Fortunately you haven't seen the page after page full of whiny know-betters insisting that their friendly regular Google and MSN bots from China and the Russian Federation really shouldn't have been blocked by that nasty bad plugin. Good riddance to those pages. As it is, collaborative, volunteer projects are two-way contracts: the author is available to reasonable requests, while the users provide useful feedback and minimize being unshaven and unwashed PITAs, like the pests that BB keeps out.
Anyway.
There's a fundamental difference between using (what I call) a remote blacklist and a local blacklist: the former implies a request (as brief and fast as it is, akin to DNS queries) while the latter just plain smacks the door in the face upon sight. So, if you're particularly hard hit by bots, a local blacklist probably is the better short-term solution. Then again, neither of the two is an adequate solution for DDoS script kiddos, when they're hellbent on making their two-bit sentiment felt. Plus, another downside of a local blocklist: it should to be regularly maintained, while a (remote) blacklist is usually very regularly updated.
Besides, neither local or remote blocklists won't do you good against determined efforts aimed specifically at the site; it's, just like BB and Akismet and Project Honeypot and others, a 99% solution, not a 100% one - obviously.
Peace (and bot-pests) out.
nv1962