A decade ago, companies had more choices about how to handle angry customers. Perhaps it was through an apology letter or an envelope stuffed with coupons. Maybe some firms chose not to deal with angry customers at all. But the times they are a-changing. Today a maddened customer can tweet or blog their discontent to anyone with an Internet connection, making social media monitoring a must for any company. Here are four strategies for approaching the angry, the irate, and the just plain mad.