[justaguyhere]

becomes more established it's relationship with sellers inevitably turns adversarial.

It is not just the market places though, isn't it? Twitter used developers to grow (generous API limits) then cut them off, tumblr used erotica to grow then started restricting, google allowed certain ads at the beginning then added restrictions... and so on.

How much regulation can you put in place for such behavior? Also regulation is expensive, selective and can be rolled back when the next gov comes along.

Would be nice to have some kind of decentralized solution for this...