I noticed my image-focused website has taken a heavy hit in impressions (and thus, clicks & traffic) for Google Images keywords from Aug 14 onwards, according to Google WMT. The average positions for keywords that have been stable for months have dropped signiicantly.
Incidentally, I made no change to the website whatsoever this month and 2 weeks prior to the change.
For the past months, I have been using a referer-based switch to deliver a hotlink warning image (of same dimensions) if the image is not requested within the html of my domain - preventing Google Images from misusing my fullsize images (and users from downloading these images all too easily).
As I have not made any other change, I can only suspect this hotlink switch is the reason for the downranking. Has anyone else made a similiar observation, or are rankings holding steady for people who use similiar hotlink protection? I could not find any info on a respective Google update.
What would you suggest to counteract this problem? Blocking hotlinking outright, instead of delivering another image? Letting Google Images crawl smaller versions of the image only?