Its amazing that Amazon has gotten away with this for so long without being hammered with antitrust violations.

The idea that a marketplace could turn around and sell their own products that directly compete with third party sellers is insane. Come to think of it, I assume Walmart would fall into this problem as well.

Every retailer I can think of (Kroger, Walmart, Costco, Target) maintains private label branded products that are sold alongside competitors.

Not every retailer's primary service is allowing anyone to sell whatever in their stores.

Amazon is more similar to a flea market organizer that sets up their own massive both. They can put their items in front of customers first and decide what to sell based upon what they see people carry away.

The biggest retailers, Walmart and Target and Kroger, allow anyone to sell whatever on their website/app. Same as Amazon.

And Kroger's branded products are almost always cheaper. Oh, the humanity!

FTC's whole yearly budget is under half a billion, Amazon and the rest can very easily throw more lawyers at a problem.

You'd think the government would be the Goliath in this battle, but it's the other way around. FTC is more of a nuicanse than an actual problem, and it's gonna remain that way for as long as FTC keeps operating on a shoestring budget.

The “marketplace” is the internet. Anyone can make a website and sell goods, with the same amount of effort as going to Amazon.com

Right, just like anybody can spin up their own copy of Myspace. Monopolies most frequently form over either cornered resources (not the case here) or network effects (bingo).

What network effects? You type in www.sellerX.com, click pay, and receive purchased item. Zero other entities involved other than buyer and seller, which means no network effects.