Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include —
(1) the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of the copyrighted work.
The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors.
Note that whether the copyright owner objects or not is not a factor to be considered when determining fair use. That copyright owner could file a lawsuit, but the fair use claim is evaluated on these four factors only.
So how does Google Print stack up against the four factors?
(1) Purpose and character. Commercial vs. educational is singled out here, and certainly Google's use is commercial. But that's not the only purpose or character allowed to be considered. A lawyer for Google could claim that their service, meeting people's information needs and directing them to a copyright holder when a work meets that information need, is a Good Thing. They could then go on to argue that making money of this is secondary, but lots of folks wouldn't believe that.
(2) Nature of the copyrighted work. This is hard to pin down due to the scope of what's being digitized. Books that have been out of print for 45 years and aren't widely available in the used book marked would evaluate differently according to this criteria than Harry Potter. (Yes, research libraries collect fiction too.)
(3) Amount of the work. Again, tricky. Google is digitizing (copying) the entire work, and, presumably, using the entire work to create their index. The counter-argument seems to be they're only showing a small part to users of their service, but I don't believe that applies here. The exclusive right is the copying part, not what you show to other people.
(4) Effect on the market. Here is where only showing snippets to end-users comes in to play. Certainly the effect on the market is potentially severe if one could download, print, read a whole book from Google instead of purchasing it. The recording industry feels that way about file sharing, but there are many who disagree, claiming file sharing actually stimulates purchasing. (Sorry no citations right now, but there are gobs of studies out there on both sides of this issue.) I imagine Google would claim that by showing snippets they're telling users about resources they didn't know about before, and are thus adding to the market. This will be an interesting argument to follow.
My conclusion is that the fair use claim is far from a slam dunk in either direction. Personally, I'd love to see this litigated (and found in favor of Google!) to start what I consider to be much-needed reform in copyright law.
IANAL. Any misinterpretations or flawed analyses are entirely mine, and the result of me trying to pretend I know something about this stuff.