[jjav]

> But where is the dividing line between market research and collusion?

Scale and ubiquity make all the difference in the world even if it seems like the same public data.

An example that comes to mind, different topic but somewhat analogous: cameras recording activity in public spaces. Some people argue there is nothing different happening today from decades ago because if you are doing activities in a public space anyone could record you just fine whether 50 years ago or today.

But they are wrong, it is vastly different. Fifty years ago someone could record you in that public space, but the odds were infinitesimally small that someone actually did. And if they did, the odds of anyone else finding that video were smaller yet. Today with ubiquitous cameras everywhere recording everything all the time it's a near certainty that you are being recorded in public spaces. And with all that video going into "the cloud" and usually available to every government agency, it's all analyzed and indexed and thus searchable at a scale never before imaginable.

Long-winded example to show that scale makes all the difference even if the underlying action is the same. Sure, some landlords have colluded with some others for centuries, but the ability for all of them to collude on every property real-time is a fundamental shift.