Blacklisting wouldn't really help as the spammers tend to go through many other sites as well. A couple of solutions were presented here, Recent Mass Football Spam. Most active mods on SE and the staff are aware of the problem as it's SE wide and it has happened in the past.
Previously, I used to drop all spam accounts into one master account and then ban it. Now since this isn't recommended, I just destroy/delete the un/registered accounts, which really doesn't help in tracking the problem. Tim Post has noted that from now on, mods will have to annotate destroy/delete actions
A big mistake we have made in the past is not fully utilizing the signal that we get from moderators and the community when destructive actions are taken. We know when moderators destroy or delete accounts, but we don't know why they did it, at least not programmatically. A change working its way through implementation now tracks this by doing something remarkable, we actually ask them to indicate a reason for the action.
Just continue flagging as normal or ping a mod in Google-Fu