lucy24 - 11:27 am on Feb 3, 2013 (gmt 0)

Block them in robots.txt from indexing your images in the first place.

You mean "block them from seeing your images", right?

Interesting hypothetical question there. If they know the image exists, and they can read its alt and the nearby text, will it show up in image searches?

Cursory investigation --looking for images from my ebooks directory, which has been off limits to the imagebot for ages-- suggests that a robot block alone may really work. At least sometimes.

If you don't want hotlinking from a search engine, why let them index the images?

Uhmm... Because you want the search engine to show a cached thumbnail, which in turn will lead people to your own site? Seriously now, isn't that like saying "If you don't want the search engine to show a preview, why let your page be indexed"?