BTG, a London-based IP firm, has filed suit against Amazon.com, Barnesandnoble.com, and two other Net companies for infringing on patents...the suit, filed in the U.S. Federal Court in Delaware, alleges that the companies use BTG’s patented technology as part of their online marketing programs. The suit asks for unspecified damages for past infringement and injunctions against future use of the technology.

BTG has charged Amazon, Barnesandnoble.com, online movie rental service Netflix, and shopping site Overstock.com with infringing U.S. patent number 5,717,860. Additionally, it charged Amazon and Barnesandnoble.com with infringing U.S. patent number 5,712,979. Both patents relate to technology that enables the tracking of users between Web sites and were acquired by BTG from personalized Web information provider Infonautics in 2002.

Some more details here…