I ran a report and found several sites in the content network that had 1 impression and 1 click. I checked some of the sites and couldn't see any of my ads - in some cases they were not even related to the same niche.
Would you view this as abnormal?
There were also some sites with low impressions but extremely high CTR that represented $1000+ CPM (none of the ones I am talking about converted and some of them had multiple clicks within a very short timeframe). In one situation, there were 4 clicks within latest visitors stats.
Also, just wondering if Google have determined invalid clicks, how long would it take for an adwords user to receive the credit back into the account? (Or do we have to pursue it and produce stats showing what we believe to be invalid).
For the same cases you have mentioned, exclude them instantly. And you need to check which keywords tiggered the ad showed on irrelated site. Then try to move positive to prevent it.
And you always be able to told Google your detections/doubts. I do think you will give more regards to your business than Google.