intellectual-property patents
What does this mean for these things to be patented by Amazon if other companies use same technology?
<p>Looking at these US Patents filed by Amazon.com:
[<em>6,853,982 - Content personalization based on actions performed during a current browsing session</em>|
<strong>Internet-based customer referral system, U.S. Patent 6,029,141, February 22, 2000</strong>|
<em>Method and system for integrating transaction mechanisms over multiple internet sites, U.S. Patent 6,882,981, April 19, 2005</em>|
<strong>Use of product viewing histories of users to identify related products, U.S. Patent 6,912,505, June 28, 2005</strong>]</p>

<p>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!</p>

<p>There are several possibilities: One, these companies have paid an unknown amount for a license. Two, since you cannot patent the effect achieved by an invention but only the way to achieve that effect, it is possible that these companies found a different method to do the same thing that Amazon has patented. Third, patents are sometimes very specific. It may be that companies do something that is very similar to what is patented, but not actually the same. Fourth and fifth, companies might not be aware of the patent, or might be convinced that they won't be caught. Sixth, they might for some reason have the idea that they could win a court case. </p>

<p>In the three patents that you quote, (two) and (three) seem likely. It also happens that companies believe quite strongly that (two) or (three) apply, and the patent holder might believe this as well, but they agree that a license is purchased for an undisclosed amount - which might be $1. If (a) Amazon tells you that they have a patent, or (b) Amazon tells you that they have a patent and Google has licensed it, (b) sounds more impressive. </p>
