Hmmmm.... There goes my head again. :-)
LMAO!! Maybe that is also how petunia gets her house so freakishly clean. It must be magic!!
As far as that goes, what WAS the original bargain between DD and Petunia?
In the first book Harry is left on the Dursley's doorstep with nothing more than a letter -- and the Dursley's took him in. Why? They obviously didn't want him and could have easily hid the letter and called social services (or whatever they are called in England.)
Then there is the Howler that DD sent Petunia in OOTP. "Remember my last!" I definitely feel that Petunia is going to be figuring more in the next book... but in what way, I have no idea.