Trailblazer looks good. As broadband speeds increase more and more graphics - in this case thumbnails, will be used to communicate to the end user. Disk space is becoming less and less a factor.
Some additional examples of the usage of thumbnails is the Firefox extension/plug-in
Better search that bring up thumbnails of the searched pages.
Also look at
Browster and
Cooliris which prefetch links and show you a thumbnail of the web page on a mouse over.