Looking at these US Patents filed by Amazon.com: [6,853,982 - Content personalization based on actions performed during a current browsing session| Internet-based customer referral system, U.S. Patent 6,029,141, February 22, 2000| Method and system for integrating transaction mechanisms over multiple internet sites, U.S. Patent 6,882,981, April 19, 2005| Use of product viewing histories of users to identify related products, U.S. Patent 6,912,505, June 28, 2005]
It seems to me that a lot of other companies also use these technologies? So, what does it mean if Amazon has these technologies, but other companies are using them? I thought if Amazon has it patented, other companies using these systems like Google, Facebook, etc. need to obtain permission? Thanks in advance if you can explain this!