I've been imagining the programmers of this CLD filter lately, especially since the Great AmEx Website Downtime of last week. Just picturing them fine-tuning it... "We've run the filter over and over again and still need to cut a load of available credit. So today we've set it to CLD anyone whose name has the letter S in it or whose birthday is in March. Anyone whose birthday is in March AND who has an S in their name is obviously a very bad risk indeed, so we're going to close their accounts outright!"
It really doesn't seem to be much more sophisticated than that, based on the evidence I've seen around here.