Amazon was very protective of its signature purchase-streamlining feature, famously suing Barnes and Noble when the latter put a similar one-click shopping option on its website back in 1999 -- a month after Amazon was granted the patent, CNET points out. Thereafter, companies took the option to license the tech from the online shopping titan. One-click has become an increasingly important part of Amazon's streamlined purchasing experience, powering its Dash buttons and voice ordering on Echo devices (and even a gimmicky promotion with Italian automaker Fiat).
But now that the patent's expired, there's nothing stopping competitors from integrating "one-click" purchasing on their own sites. It will be interesting to see if feature gets people buying wildly popular items like sneakers or the SNES Classic on vendor sites alone instead of wandering over to price-match on Amazon.