I'd also say that Google's caching is a copyright violation, and should be opt-in. Google seems to have this notion that because they're above the law when it comes to copyright. They're not. They may be doing this for good reasons, and it may have positive effects for the users of their search engine, but that's irrelevant. The law is the law.
Also, I never said that it was evil. I only said that they shouldn't do it. There is a wide gap between those two assertions.
*Edited to change "provide text" to "provide context" at the end of the first paragraph, and remove an unfortunate use of all caps. Wasn't thinking as clearly as I should have been, sorry.
It's a large thumbnail where the text isn't legible at all outside of a few select words and the extracted surrounding text. This isn't the same as providing a full-page preview with Google wrapping it in an iframe, for example, to get advertising revenue. People still have to go to your site to read anything outside of the contextual text.