After I posted my first post about invalid click - regarding the "adsense pirate" email that I got, I now see that about $2 and some change was deducted from my adsense earnings because of invalid clicks.
It worries me though in case adsense might consider disabling my account although I have gotten a response from someone here who says that Adsense deals with this kind of thing all the time!
The solutions that adsense provides for helping to stop invalid clicks seems so complicated and its so hard to find PHYSICAL contact information for Adsense - meaning a telephone number!
You can't call AdSense. Put that one right out of your head.
Invalid clicks (as I found out from support when I questioned a larger-than-usual deduction from my own account) don't necessarily mean clicks on YOUR end; they can also mean that an advertiser was breaking the rules in some fashion as well. (That happens almost as often as AdSense fraud, trust me) That's what apparently happened to me, and I was also told they were working on more specific descriptions when money was taken back (but obviously haven't released them yet - probly has to go through twelve levels of bureaucracy first)
$2 and change isn't much; I wouldn't worry about it. I get a little claw back every month now, and as long as it stays below a few percent, I'm not worried about it. If it starts turning into a significant percentage, then I'd shoot an email to support (and start looking at the sources of traffic I was getting)