Yesterday, April Fool's Day, Google started crediting money to my Adwords account. I was expecting to be billed yesterday, but every time I logged in, I owed them less money. Now as of this morning, they owe me money so my ads are essentially showing for free right now. My cost per click today has also dropped so I'm wondering if they think they've been overcharging me for the last several months? I've never seen this before. It is nice to have the credit, but it also worries me a bit.