Over a year ago, I wrote that the professional discounting brand Groupon had major flaws. The trade off of bigger margins for more traffic has always been bad for a brand. Customers learn never to pay full price for your goods. Although Groupon's paying customers may not have known this at first, I knew they would eventually wise up (like these angry customers).
Now, it looks like investors in the daily deals site have finally learned this as well.
As an aside, the same thing is happening at Facebook. These examples serve as more evidence that fundamental marketing principles still apply in the much hyped social-media world.