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It was a new listing, there were no other clicks in weeks after, though there were many views of it. The 300% CTR sort of says it all! Contacted Adwords support staff, they say that "flooding" is blocked.... someone else must have clicked also... 3x the number of views in a minute (well it took about 10 minutes to register, but then no other clicks for over a month!)
A little scary - someone could really run up a bill on a competitor with an itchy clicking finger!
How'd you figure this out? (Er..how did you first notice this?)
Now in all fairness to Google, they may have fixed this, it was over a month ago that I warned them (and they said it wasn't true).
But how else do you get a 300% CTR?