There seems to be long cycles of innovation -> consolidation -> fragmentation on the Internet. Startups sprout up -> a 'winner' emerges -> then the big, established players decide they want in, and develop their own competing services. It's happened with:
* streaming music (myriad startups -> Spotify -> GooglePlay, Amazon Prime, Apple Radio etc)
* games services (startups -> Steam emerges -> EA Origin, Ubisoft Uplay, Blizzard Battle etc)
* video-on-demand (startups -> Netflix -> HBO GO, Amazon Prime etc)
* social media (startups -> FaceBook -> Lots of failing attempts to muscle in)
I suppose the same will happen with shopping. At present, lots of companies import goods to NZ to on-sell, but if Amazon really sets up Australasian shop, we may need only one. Until Google of Facebook decides they want in, and the market fragments again...
I'm inclined to think services like PriceSpy, the sites that tells you which streaming service have which programmes, which provider has the best electricity rates or mobile phone deals, are a response to the hassle of fragmentation/competition.