I have said it before, and I'll say it again.
Google is the largest content scraper in the world, and they don't care that the content is being abused and stolen. Images especially.
They have one thing in mind. Keep the users eyes as long as possible on the Google site, where they potentially click on ads. Google has NO interest, financial or otherwise, in sending users to actual web-sites unless they absolutely have to, or if they clicked on a paid ad.
By allowing Google to steal all images, one is in effect saying that it is OK to steal.
Also, as I mentioned, watch your logs.. Visitors that arrive from the Google image search behave differently IF they ever get to your site. They might look like visitors, but not all visitors are created equally.
First, the keywords they arrive on match the image, not your article text. That tells you what their real interest is.
Secondly, they do not move as do other users. They obviously landed on your site, merely to do a right-click if the image is good enough. Arrived merely to steal an image.
By busting frames and similar, Google is accomplishing again the same. If they have your real (full-size) image, the user can steal it directly from there. No need to even visit your site. And again, it keeps users on the ad-filled Google site longer.
All in all, good statistics for Google. They are not in the business of helping visitors find content as a "search engine" anymore. They are in the business of being traffic cop, making sure that users click on as many ads as possible, to deliver PAID traffic to the sites that can afford it.
The only time Google still acts as a search engine is when you search for very technical topics. Less ad-relevance there. But instead, they show a million copy-sites where people have duplicated Unix man-pages, wordpress/joomla/.... PHPDoc type content onto the Internet to "create content", with no value add. No effort on Google's behalf to skim off the junk sites. Instead you must wade through all the crud-sites manually.
And the more friendly web-site owners are, the better for Google. Just watch their current stock-price. Up around 30% over the past months. Soon almost back up to the $700 level again. All the Google preview, frame-busting, and other "keep people on Google" is working. And it will keep working until we all say NO.