I Just go for the gold and avoid the headaches, if a bot, robot, or an SE crawls my site excesively, I lookup the IP it came from, get the info I need, which is the company name and IP range, then I simply ban the entire IP range. My robots.txt is configured to prevent any SEs from browsing any restricted areas, however, both SLURP and GOOGLEBOT both do "ALOT" of crawling, and they often look for URLs and Subdirectories that do not exsist, which uses up alot of bandwidth...
I have been using this proccess for about a week now and it has freed up alot of bandwith...
Unfourtunatly, both Google and Yahoo are blocked, However, I am not worried about it, Google still has my original site cached from a year and a half ago, and I am still using the same URL, so it all evens out :D ...
Just thought this might help y'all out.
-- The DEVI8OR