Interesting as Apple clearly copied the look and feel of Wil's application Delicious Library of use in thier iBook store application. Granted I doubt Wil holds a patent on that interface, but it does seem a bit hypocritical.
Either that or somebody at Apple once went to a library. Wood shelves holding books... profound.
If you read more into it, the iPad team is where 3 Delicious Monster employees ended up, including the lead designer.
Trademark law refers primarily to the design of nonfunctional things such as logos, the Deep Note sound, etc.
Edit - Looks like i'm wrong. (easier to edit than respond to 4 other posts)