“(multi-format listings — auction/BIN/offer mixed in search results)”
Mixing auction listings, Buy It Now, and "Make an Offer" in the same search results creates cognitive load that Amazon and Walmart.com avoid entirely. A buyer looking for a specific product has to interpret three different purchasing mechanisms on one page.
“Default search results to Buy It Now with fixed pricing. Surface auctions and offers as optional filters for buyers who want them, not as noise for those who don't.”
Reducing purchase-mechanism ambiguity in default results makes eBay feel as simple as Amazon for the 85% of transactions that are already fixed-price.