As the article states, it started with the button, which, as you quite rightly point out, dominoed into a lot of changes and thinking about edge cases that didn't exist before. The point I was trying to make was that it started with the button.
The big story here isn't that adding this particular button will yield $300m in revenue. The story was that, by watching users, we saw an opportunity to reap $300m. And we took it and it worked.
Without that, the article does seem to claim that just changing the label of the button had that effect.
And that was the point.
My post was motivated by the fact that the article is written as if this was a trivial change - "The designers fixed the problem simply" - and it really was not (for the developers).
"We took a simple idea and made $300million more dollars" - Yes.
"We did something simple and made $300million more dollars" - Not even nearly.
I am really not sure what assumption you think I am making is wrong?
I doubt it was that simple. The UX flow changes if you can purchase as a guest.
More importantly, I expect when the system was built, the developers asked if all orders had a user, received the answer 'yes', and accordingly built that into the system.
Then one day some consultant comes along and pronounces that 'not all orders have a user now, please implement a guest checkout'.
So the developers probably needed to recode the whole flow, possibly remove some foreign key constraints, allowing a user to only partially exist (which needs to reconcile with a real user later if the email matches an existing user later).
And what if they don't create an account at that time, but they do later, should all orders to a given email then get attached to that account?
Are there privacy issues around this? Can we assume an email address belongs to an individual, I am not sure you can.
All this for a system that is processing millions of dollars in orders. So regression testing and deployment, would have to be done very carefully.
This is all just what I can think of off the top of my head.
So, with respect, you did not just change a fucking button.