I think the replacement of incumbents is interesting. You have the classic AirBnB from Craigslist. I think that's in their founding story. I also use an app cal

I think the replacement of incumbents is interesting. You have the classic AirBnB from Craigslist. I think that's in their founding story. I also use an app called Reverb. It is basically a sliver of Craigslist or Ebay. I'm not sure what other examples are out there but I bet there is still more meat on that bone. :) Certainly these sites are one-to-one replacements but they are taking out a section of the incumbent site.