Here's a link to a discussion of HP inkjet printers and printers cartridges with smart chips. Apparently the chips cause a cartridge or print head to "expire" after a certain date, forcing the user to replace the part or the printer, even if it is working perfectly. I'd never heard of such a thing and wonder what other manufacturers are doing the same thing.
http://www.gripe2ed.com/scoop/story/2005/5/23/01334/5457
http://www.gripe2ed.com/scoop/story/2005/5/23/01334/5457