It wouldn't be as much use as you think. The blacklist isn't for the entire account but the suspension that follows it (assuming people reported the spammer) does lock the entire account. Don't underestimate the RMT. They happily create brand new accounts and highjack legit accounts. You can tell by the number of people in your blacklist that actually read as "DELETED" how often they actually delete a character and recreate them on the same account. It isn't often. They're more likely to use all the chars available on the account all at once on different servers.