Anybody else have the same experience, or have suggestions on how to prevent this from happeneing?
I would not be too concerned. That being said, I _WOULD_ contact google support just to make sure.
You'll not be billed more than your daily budget times the number of days for which you are billed.
Basically, you'll be credited for any extra clicks beyond those which your daily budget allowed. And since the clicks have already been delivered, those 'extra' clicks become free.
There is a brief note on this in the AdWords FAQ. Please see #6, here:
[adwords.google.com...]
By the way, an overdelivery such as you describe is a very likely sign that your daily budget is too low - and that your ads are most likely not showing all the time. You might want to check the 'Recommended budget' link on the 'Edit Campaign Settings' page, in each campaign.
One way to reduce the recommended budget, btw, is to get rid of non-performing or low-performing keywords. Then your ads will show more often for the remaining keywords, for the same budget.
AWA