Arts Technica provides an excellent overview of a 2004 case that has Google on the receiving end of a preliminary injunction over image search results. Google – and Amazon, which has also been sued – have relied on Kelly v. Arriba Soft, where the 9th Circuit Court ruled that search engine thumbnails were legal. (pdf)
Copyright holders have held the trump card in recent skirmishes. A 1709 law set copyright for 14 years. Prior to 1976, copyright was granted for 28 years and renewable for another 28 years for a total of 56 years. Then the 1976 Copyright Act boosted the term to 75 years.
The 1998 Sonny Bono Term Extension Act extended the copyright to 95 years for corporations and 70 years after death for individuals.
And then there is the Digital Millenium Copyright Act . Stay tuned.