An advertiser brought to my attention today that their regular automatic statistics report showed a huge spike in impressions and clicks for their ad on 2 days during the reporting period and was wondering what that was about. Like they usually get 0-5 clicks per week and the report shows 450 in one day. We didn't have a commensurate spike in web traffic that day so I'm not sure what to tell him. Has anyone found a likely culprit for an inexplicable spike in the clicks report? I hate to undermine our advertisers' trust in the data we're showing them on their ad's performance.