There's an interesting WSJ piece entitled "Compass Sues to Stop ‘Zillow Ban’". In short, two real estate titans are battling it out in court over what is, in many ways, a data access issue.

This is only somewhat related to the article's point, but, Compass's "private listings" remind me of dark pools in trading:

*These types of sales, called “pocket listings,” “whisper listings” or “private listings,” have long been a source of contention among brokerages, because real estate listings are precious currency. *

Compass’s practice, since the fall, has been to show many of its so-called private listings only to fellow Compass agents, hidden from Zillow or other search portals. Competitors have accused Compass of hoarding listings in the process.