This may sound a bit draconian, but I'd even suggest something like if you're blacklisted by more than a few hundred people during a 24-hour period, you get at least a mute, possibly even a suspension.
I think you've mentioned something like this before Thayos and I completely agree.
It's pretty easy to define "spamming" activity. If it's not already in the ToS (I believe it is in some form), SE should add a clear definition. Then, automatically lock down characters that shout multiple lines of chat every few seconds or send tells to large numbers of players -and- at the same time seem to rack up a lot of \blist requests. This can all be scripted to happen in code on their end.
I find it hard to imagine someone accidentally meeting those requirements together, and possibly SE could quickly review chat logs to see if there was an error in the lock-out. Not rocket science really.