I don't work for Google, I'm not an attorney, and I'm not defending Google's right to do anything. (A lawyer might point out that Google Image Search has previewed entire works for quite some time, though.)
Also, debating what search engines should or shouldn't do is less productive than finding ways to profit from the choices that they do make. If Brett's "mouseover" scenario does come to pass, it's likely to benefit Web sites with real content and user-friendly presentation. This might be a good time to think about the question, "How can I maximize my search-engine referrals if Google Web Search offers searchers a WYSIWYG experience?"