I've heard the same argument time and time again when I was still working for an ISP and involved in spam-fighting back in the 90's. Reality is, you have to to

I've heard the same argument time and time again when I was still working for an ISP and involved in spam-fighting back in the 90's. Reality is, you have to totally ignore complaint after complaint about spam coming from your network before you end up on any blacklist. Most common form of negligence often came from some management decision to let role accounts like abuse@ get handled by non-technical communication or support people with zero authority to escalate the problem. If that still happens in 2013, fuck them. Bottom line is that only willful negligence or deliberate support to spammers can get you blacklisted. If you are in no hurry to remove spammers, don't expect Spamhaus e.a. to be in any hurry to un-blacklist you.