Here is a nice article about the unreliability of blacklists: http://www.theregister.co.uk/2007/07/08/blacklists_are_baaad/
Everyone that knows how easy it is to craft new identities can imagine how useful blacklists are. Hence, we tried to stay away from them in our IETF GEOPRIV Common Policy work and the recent work on avoiding Spam for Internet Telephony.
Unfortunately, many policy langues support black lists as one of their core features. Typically, the consequence is that strong identity mechanisms do not get deployed since users are given the impression they already have all the tools in their possession.