Legality and thumbnails
I am fond of the argument that a thumbnail is to a picture as a summary is to a text -- both should be protected not only as fair use exemptions to Title 17, but also by the inaleinable rights of citizens in a free society to discuss ideas freely. Not all would agree with me. Here are some perspectives on both sides of the issue.
Ditto.com -- is a searchable site which redistributes thumbnail images found on the web.
See here for discussion of a court case concerning ditto.com's use of thumbnails.
Here is a reference to the first court's decision which finds:
On apparent first impression, the Court holds the use by an Internet "visual search engine" of others' copyrighted images is a prima facia copyright violation, but it may be justified under the "fair use" doctrine. The Court finds that, under the particular circumstances of this case, the "fair use" doctrine applies, and the Digital Millennium Copyright Act is not violated.
While the language used here is careful to avoid generalization to other circumstances, critical issues in the fair use analysis included the non-reproducibility of the original from the thumbnail and plaintiff's inability to document financial damage from the copying.
A presentation of the 9th Circuit which, on appeal, affirmed the "thumbnail part" of the lower court's finding can be found here. Importantly, the court ruled that
The most significant factor favoring Defendant is the transformative nature of its use of Plaintiff's images. Defendant's use is very different from the use for which the images were originally created. Plaintiff's photographs are artistic works used for illustrative purposes. Defendant's visual search engine is designed to catalog and improve access to images on the Internet. The character of the thumbnail index is not esthetic, but functional; its purpose is not to be artistic, but to be comprehensive.
The Architecture Slide Library at U.C. Berkeley, has produced the document Digital Images and Fair Use Web Sites as seen at www.utsystem.edu/ogc/intellectualproperty/portland.htm .