[malloci]

Isn't Amazon's marketplace similar in that regard? They compete with other sellers using Amazon's platform all the time.

Ethically, it seems a bit fuzzy for me given that one of Zillow's big features is there zEstimate. How can they demonstrably prove they aren't tweaking that somehow for their own gain?

[jacobkranz]

I'd argue that Amazon's customers are the buyers of the products, not the sellers using Amazon's platform.

[bunderbunder]

I'd argue that Amazon has many different groups of customers.