Because if an "invention" is obvious it isn't patentable ( http://www.bitlaw.com/source/35usc/103.html ), and many many people see this as being far too obvious to be patentable.

"Obvious" for patentability purposes means obvious in advance, not obvious in hindsight. Before Amazon, nobody had one-click purchasing. They wanted people to sign up, to fill out forms with irrelevant info, and "engage with the customer". After Amazon, many people wanted one-click. That means it wasn't "obvious to one skilled in the art" in advance. For patentability purposes, the best way to demonstrate non-obviousness is to show that lots of people have worked on the problem and didn't get it right. The one-click patent meets that test.

Amazon's real innovation was combining one-click ordering with easy order cancellation for a few minutes after the order. This makes enabling one-click ordering low-risk. Many on-line sales operations still don't get this, as I mentioned the last time this came up on HN. Most shopping cart programs have a built-in attitude of "We have your money now, muhaaa haaa". Yes, you can "contact customer service to cancel." ("Please listen carefully as our menu options have changed... Due to unusually high call volume...")

Now the people who don't get this will implement one-click ordering without easy cancellation and anger their customers.

  > obvious in advance, not obvious in hindsight

Thanks! That's what I was looking for. Many things we take for granted, which are so simple and obvious, are not obvious at all when they don't exist... I remember exactly those experiences everywhere - you have to register to add an item to a shopping card... And yes, you MUST give us your mother's maiden name...

Additionally, the meaning of "obvious" is non-obvious. It means obvious to somebody with knowledge of the relevant field.

Which, in my estimation, makes this "invention" even MORE obvious.