eWeek reports that IBM is suing Amazon over the alleged infringements of 18-year-old patents relating to online shopping.

The patents that IBM says are being violated are U.S. 5,796,967: Presenting Applications in an Interactive Service; U.S. 5,442,771: Storing Data in an Interactive Network; U.S. 7,072,849: Presenting Advertising in an Interactive Service; U.S. 5,446,891: Adjusting Hypertext Links with Weighted User Goals and Activities; and U.S. 5,319,542: Ordering Items Using an Electronic Catalogue.

Of course, the point of patents is to ensure inventors get the benefits of their inventions but these all sound a bit vague and illustrate the dangers inherent in the patent system.