They seemed to be jacking with my reports (visitors were about the same each day, but earnings were extremely erratic) for about 2 to 3 months right before they decided to disabled my account for undisclosed reasons and keep my earnings for themselves. (They did this right before they were supposed to be sending me a check. If you do a search on "Adsense Scam," you'll see that this is a common tactic they use whenever they owe someone money and don't want to pay.)
There are plenty of articles expressing skepticism about Google not registering hits accurately if you look on-line.
They are absolutely not to be trusted.