Senior WebmasterWorld member, incrediBILL, started a thread at WebmasterWorld expressing his concern over bots and crawlers that may cause his ad impressions with Google AdSense be increased.
Both Ask and Snap make screen shots of various pages in your site so it's not just a single home page image we're talking about. Snap has attempted to make upwards of 40K screen shorts on my site alone before I stopped counting. Ask seems to be a little more conservative in the quantity of their screen shots, but that could be growing pains as it remains to be seen if they'll screen shot entire sites and/or all sites they index.
Since some bots are generating impressions on your ads, that will impact your CTR and possibly hurt your metrics both as a publisher and even as an advertiser.
Google's AdSenseAdvisor did come by to say he or she would get us an answer from Google soon. But another member makes a very valid point, "Why would a screenshot be taken of more than your front page?"
We will watch the thread and report back Google's response when we see it.
Forum discussion at WebmasterWorld.