If those would routinely abuse the power bestowed upon them, they would threaten the magazines. Its in there own best interest to not abuse there review-powers,

If those would routinely abuse the power bestowed upon them, they would threaten the magazines. Its in there own best interest to not abuse there review-powers, or there reputation could be ruined by the very same marketplace. You cant just open another marketplace at the same location, because that has you at a automatic disadvantage. You could however ruin the marketplaces reputation, trying to shift customers to yours. You can also, wrap the market-place as in- provide a vital layer they need to function, and thus turn them into a organella of a bigger market-place.